Attachement 12 - 250722 - GEOTECH - 3065-I 02R LAVA Police 11-10-23.pdf

GEOTECHNICAL INVESTIGATION

PROPOSED POLICE BUILDING

DEPARTMENT OF VETERANS AFFAIRS

WEST LOS ANGELES MEDICAL CENTER

EISENHOWER AVENUE

LOS ANGELES, CALIFORNIA

Prepared for:

Spees LLC

625 1st Avenue, Suite 301 Seattle, Washington 98101

Prepared by:

Geotechnical Professionals Inc.

5736 Corporate Avenue Cypress, California 90630

(714) 220-2211

Project No. 3065.I November 10, 2023

3065-I-02L (11/23)

November 10, 2023

Spees LLC 625 1st Avenue, Suite 301 Seattle, WA 98101

Attention: Mr. Ray Spees, P.E.

Subject: Report of Geotechnical Investigation Proposed Police Building Department of Veterans Affairs West Los Angeles Medical Center Eisenhower Avenue Los Angeles, California GPI Project No. 3065.I

Dear Mr. Spees:

Transmitted herewith is a PDF copy of our report of geotechnical investigation for the subject project. The report presents our evaluation of the foundation conditions at the site and recommendations for design and construction.

We appreciate the opportunity of offering our services on this project and look forward to seeing the project through its successful completion. Feel free to contact us if you have any questions regarding our report or need further assistance.

Very truly yours, Geotechnical Professionals Inc.

Patrick I.F. McGervey, P.E. Donald A. Cords, G.E.

Project Engineer Principal

Spees LLC November 10, 2023 Proposed Veterans Affairs Police Building, Los Angeles, California GPI Project No. 3065.I

3065-I-01R.doc (11/23)

TABLE OF CONTENTS

PAGE

1.0 INTRODUCTION 1

1.1 GENERAL 1

1.2 PROJECT DESCRIPTION 1

1.3 PURPOSE OF INVESTIGATION 1

2.0 SCOPE OF WORK 2

3.0 SITE CONDITIONS 3

3.1 SURFACE CONDITIONS 3

3.2 SUBSURFACE SOILS 3

3.3 GROUNDWATER AND CAVING 3

3.4 GEOLOGIC – SEISMIC HAZARDS 4

4.0 CONCLUSIONS AND RECOMMENDATIONS 5

4.1 GENERAL 5

4.2 SEISMIC CONSIDERATIONS 5

4.2.1 General 5

4.2.2 Strong Ground Motion Potential 6

4.2.3 Liquefaction and Seismic Settlement 8

4.3 EARTHWORK 8

4.3.1 Clearing 8

4.3.2 Excavations 8

4.3.3 Subgrade Preparation 10

4.3.4 Material for Fill 10

4.3.5 Placement and Compaction of Fills 11

4.3.6 Shrinkage and Subsidence 11

4.3.7 Observation and Testing 11

4.3.8 Trench/Wall Backfill 11

4.4 FOUNDATIONS 12

4.4.1 General 12

4.4.2 Allowable Bearing Pressures 12

4.4.3 Minimum Footing Width and Embedment 12

4.4.4 Estimated Structural Settlements 12

4.4.5 Lateral Load Resistance 13

4.4.6 Light Standards and Poles 13

4.4.7 Foundation Concrete 13

4.4.8 Footing Excavation Observation 14

4.5 BUILDING FLOOR SLABS 14

4.6 LATERAL EARTH PRESSURES 14

4.7 CORROSION 15

4.8 EXTERIOR CONCRETE AND MASONRY FLATWORK 15

4.9 PAVED AREAS 16

4.10 STORM WATER INFILTRATION 17

4.11 GEOTECHNICAL OBSERVATION AND TESTING 17

5.0 LIMITATIONS 18

REFERENCES

APPENDICES

A EXPLORATORY BORINGS

B LABORATORY TESTS

C GEOLOGIC-SEISMIC HAZARD EVALUATION

3065-I-01R.doc (11/23)

LIST OF FIGURES

FIGURE NO.

1 Site Location Map 2 Site Plan 3 Probabilisitic MCER Response Spectra at 5% Damping 4 Deterministic 84th Percentile MCER Response Spectra 5 Site-Specific MCER and Design Response Spectra @ 5% Damping

TABLE NO.

1 Risk-Targeted Site-Specific Seismic Response Spectra Worksheet

APPENDIX A

A-1 to A-9 Logs of Borings

APPENDIX B

B-1 Atterberg Limits Test Results B-2 & B-4 Direct Shear Test Results B-5 Consolidation Test Results Table 1 Corrosivity Test Results

APPENDIX C

C-1 Regional Geologic Map C-2 Groundwater Map C-3 Regional Fault Map C-4 Regional Seismicity C-5 Seismic Hazards

3065-I-02R.doc (11/23) 1

1.0 INTRODUCTION

1.1 GENERAL

This report presents the results of the geotechnical investigation performed by Geotechnical Professionals Inc. (GPI) for the proposed police building at the Veterans Affairs West Los Angeles Medical Center in Los Angeles, California. The geographical site location is shown on the Site Location Map, Figure 1.

1.2 PROJECT DESCRIPTION

The proposed project will include a new police station building within the Veterans Park area of the Los Angeles Medical Center of the Department of Veterans Affairs (VA). The proposed police building will be located west of Building 220 and south of Eisenhower Avenue.

We were provided a Site Conceptual Plan by Spees Design Build, LLC, provided on October 5, 2023 that showed the proposed layout of the new building. We understand that the proposed building will be a two-story, steel frame building covering a footprint of approximately 12,000 square feet with associated at-grade parking for the facility.

Proposed finished floor elevations and structural loads were not finalized at the time this report was prepared. We have assumed proposed grades for the building will be similar to existing grades with cuts and fills up to 3 feet. Based on similar past projects, we assume that the column loads will be on the order of 50 to 100 kips and wall loads on the order of 4 to 8 kips per lineal foot.

Our recommendations are based upon the above structural and finish grade information. We should be notified if the actual loads and/or grades differ or change during the project design to either confirm or modify our recommendations. Also, when the project grading and foundation plans become available, we should be provided with copies for review and comment.

1.3 PURPOSE OF INVESTIGATION

The primary purpose of this investigation and report is to provide an evaluation of the existing geotechnical conditions at the site as they relate to the design and construction of the proposed development. More specifically, this investigation was aimed at providing geotechnical recommendations for planning earthwork, and design of foundations, concrete slabs, and pavements.

3065-I-02R.doc (11/23) 2

2.0 SCOPE OF WORK

Our scope of work for this investigation consisted of review of existing data, field exploration, laboratory testing, geologic and seismic evaluation, engineering analysis, and the preparation of this report. Our investigation was performed in accordance with the guidelines in the VA Site Development Design Manual (VA, 2013).

Our field exploration consisted of nine exploratory borings performed to depths of approximately 10 to 71½ feet below existing grades. A description of field procedures and Logs of the Borings are presented in the attached Appendix A. The approximate locations of the explorations are shown on the Site Plan, Figure 2.

Laboratory soil tests were performed on selected representative samples as an aid in soil classification and to evaluate the engineering properties of the soils. The geotechnical laboratory testing program included determinations of moisture content and dry density, grain size analysis, Atterberg limits, shear strength, consolidation, maximum density, expansion potential, R-value, and corrosivity. Laboratory testing procedures and results are summarized in Appendix B.

Soil corrosivity testing was performed by HDR under subcontract to GPI. R-value testing was performed by Geologic Associates under subcontract to GPI. Their test results are presented in Appendix B.

An evaluation of geologic and seismic hazards is presented in Appendix C.

Engineering evaluations were performed to provide earthwork criteria and foundation recommendations. The results of our evaluations are presented in the remainder of this report.

3065-I-02R.doc (11/23) 3

3.0 SITE CONDITIONS

3.1 SURFACE CONDITIONS

The site is located on the campus of the U.S. Department of Veterans Affairs West Los Angeles Medical Center to the west of Building 220. The site is currently occupied by at grade parking, grass and trees. To the north of the site is Eisenhower Avenue, to the east is an at-grade parking lot and Building 220, to the south is San Vicente Boulevard, and to the west is the remainder of the at grade parking lot adjacent to Bingham Avenue.

Based on a review of historical photographs (Historic Aerials), the site appears to have been graded to its current state between 1952 and 1964. Prior to 1952, the site appears to have been occupied by the previous alignment of San Vicente Boulevard. The medical campus to the north appears to have been developed prior to 1947 (earliest photograph available).

In general, the site slopes gently from the north to the south. The elevations within the site limits range from approximately +339 feet in the north to approximately +328 feet in the south.

3.2 SUBSURFACE SOILS

Our field investigation disclosed a subsurface profile consisting of minor amounts of undocumented fill soils overlying natural soils. Detailed descriptions of the conditions encountered are shown on the Logs of Borings in Appendix A.

The fill soils, encountered in our boring to depths of approximately 2 to 4 feet, consisted of silty clays and clayey silts. Documentation regarding the placement and compaction of the fill was not provided.

In general, the underlying natural soils consist Quaternary age Older Alluvial sediments consisting of very stiff to hard silty clays and clayey silts with trace amounts of sand.

The soils in the upper 10 feet of the soil profile generally have moderate strength and low compressibility characteristics. The moisture content of the upper soils encountered in our explorations were generally slightly moist to moist, ranging from about 7 to 23 percent moisture. Expansion Index testing on a representative sample of the upper onsite soils indicates the soils have a low to medium potential for expansion (E.I. of 49).

3.3 GROUNDWATER AND CAVING

Groundwater was not encountered in our borings to a depth of 71½ feet below existing grade immediately after drilling. Data published by the State of California indicates a historical shallowest depth to groundwater of approximately 25 feet at the subject site (CGS, 1998). Caving was not observed in our relatively small diameter, hollow stem auger borings.

3065-I-02R.doc (11/23) 4

3.4 GEOLOGIC – SEISMIC HAZARDS

As required by VA Seismic Design Requirements (VA, 2019), we performed a geologic hazards and site-specific ground response analysis. The geologic hazards analysis is presented in Appendix C. Ground motion and seismic settlement is addressed in the “Seismic Considerations” section of this report.

3065-I-02R.doc (11/23) 5

4.0 CONCLUSIONS AND RECOMMENDATIONS

4.1 GENERAL

Based on the results of our investigation, it is our opinion that from a geotechnical viewpoint it is feasible to develop the site as proposed.

The new building may be supported on shallow foundations following the mitigation of the geotechnical constraints discussed below. The most significant geotechnical issues that will affect the design and construction of the proposed improvements are as follows:

• Undocumented fills were reported to depths of up to 4 feet below existing grade at the site. The fill soils are not considered to be suitable for direct support of foundations or floor slabs without remedial earthwork. For the proposed improvements, we recommend removal and recompaction of the fill and a portion of the upper low-density natural soils to provide uniform support for the planned foundations and floor slab.

• The on-site soils are expansive (EI of 49) and will shrink and swell with changes in moisture content. We recommend supporting the building floor slab and concrete hardscape on a layer of select granular, non-expansive compacted fill.

• The upper soils will provide poor support for pavements, resulting in relatively thick sections for asphalt concrete pavements. For PCC pavements, a thin layer of aggregate base should underlay the concrete.

• Resistivity testing of the on-site soils indicates that they are moderately corrosive to ferrous metals. If buried metal pipe is to be used, a corrosion engineer should be consulted.

Our recommendations related to the geotechnical aspects of the development of the site are presented in the subsequent sections of this report.

4.2 SEISMIC CONSIDERATIONS

4.2.1 General

We assume the seismic design of the proposed development will be in accordance with the 2022 California building Code (CBC). For the 2022 CBC, a Soil Class D may be used. The seismic code values can be obtained directly from the tables in the building code using the above values and appropriate United States Geological Survey website (earthquake.usgs.gov). We also present these values in our Table 1, Site Specific Response Spectra Worksheet. The project Structural Engineer should determine the seismic design method.

3065-I-02R.doc (11/23) 6

Details of our geologic and seismic evaluation for the site are presented in Appendix C.

4.2.2 Strong Ground Motion Potential

Site specific response spectra were generated in accordance with the 2022 California Building Code (CBC) (Section 1613A), Section 21.2 of ASCE 7-16 (ASCE, 2017), and ASCE 7-16 Supplement 1 (2018). Creation of a site-specific response spectrum requires analyzing site-specific deterministic and probabilistic seismic response spectra in order to create the Risk-Targeted Maximum Considered Earthquake (MCER) and Design response spectra.

We calculated the deterministic and probabilistic site-response spectra using web-based tools that estimate uniform hazard spectra using faults as earthquake sources.

The web tools include geographic and seismic information on known active faults in California based on the 2014 USGS fault model. For both our deterministic and probabilistic analyses, we used four 2014 NGA West 2 attenuation relationships to determine the geometric-mean horizontal component of ground motion: Abrahamson- Silva-Kamai (2014), Boore-Stewart-Seyhan-Atkinson (2014), Campbell-Bozorgnia (2014), and Chiou-Youngs (2014).

For our evaluations, we used a shear wave velocity, VS30, of 298 meters per second (m/s), or about 978 feet per second (fps), for the selected attenuation relationships. This value corresponds to the upper range of the CBC Site Class D (stiff soil) and was estimated from SPT blowcounts obtained during our investigations at the project site.

Probabilistic Spectra

The probabilistic (MCER) ground motion spectra (per the Method 1 requirements of Section 21.2.1.1, ASCE 7-16) were calculated using the USGS Unified Hazard Tool website. Using inputs of the site coordinates, Site Class, and time horizon (return period), the web tool outputs the Uniform Hazard Response Spectrum (UHRS) for predetermined Site Classes and shear wave velocities. For our analysis, we utilized the Dynamic: Conterminous U.S. 2014 (update, v4.2.0) edition of the web tool. We calculated response spectra for 259 m/s (Site Class D) and 360 m/s (C/D Boundary) and then linearly interpolated between those spectra based on our estimated site-specific shear wave velocity of 298 m/s.

The MCER corresponds to an earthquake ground motion having a 2 percent probability of exceedance within a 50-year period, or an average return period of 2,475 years. The final probabilistic response spectrum was based on the geometric mean horizontal component, scaled by factors to convert the geometric-mean response to the maximum-rotated response, of the spectral response values at 5% damping for the four above noted attenuation relationships. The maximum rotated component (MRC) response factors used were based on the period dependent factors developed by Huang, Whittaker, and Luco (2008) and presented in Section 21.2 of ASCE 7-16. The weighted average, maximum-rotated site-specific probabilistic response for the above predetermined shear wave velocities, as well as the final interpolation based on the site-specific shear wave velocity, are shown on the attached Figure 3.

3065-I-02R.doc (11/23) 7

Deterministic Spectra

Site-specific deterministic MCE response spectra were generated per the requirements of ASCE Section 7-16. The response spectrum was generated for nearby active faults, which were determined based on a combination of proximity, previous screening using the EZ-Frisk program, and the table of deaggregation contributors developed with the USGS Unified Hazard Tool. Based on the above resources, the controlling deterministic response spectrum is predominantly based on Santa Monica Fault (Alternate 2).

Spectral acceleration ordinates were calculated utilizing the Pacific Earthquake Engineering Research Center (PEER) ground motion database and the PEER NGA- West2 Spectrum model. We utilized the four previously noted attenuation relationships (equally weighted) and determined the required input fault parameters from USGS web resources (see references). Per the requirements of ASCE 7-16, we utilized an epsilon value of 1.0 for our analysis, which corresponds to the 84th percentile of the geometric-mean component (Sa + one standard deviation) of the spectral acceleration at 5% damping. As with the probabilistic spectrum, the geometric-mean values were scaled by period-dependent factors per Huang et al (2008) to obtain the maximum-rotated response. The site-specific deterministic response spectrum is shown on Figure 4.

MCER and Design Response Spectra

The above-described analytical steps are presented in the attached Table 1, Risk- Targeted Site-Specific Seismic Response Spectra Worksheet.

The site-specific MCER response spectrum was generated per the requirements of Section 21.2 of ASCE 7-16 by comparing the spectral response accelerations from the probabilistic MCER (Section 21.2.1, see Figure 1) and the deterministic MCER (Section 21.2.2, see Figure 2), with the resulting MCER response spectrum being the lesser of the spectra accelerations at each period. The ordinates for the MCER response spectrum are presented in Table 1 (Column 11).

The site-specific design response spectrum was generated per the requirements by taking 2/3 of the risk-targeted MCER response spectrum, but confirming that the values are not less than 80 percent of the spectral acceleration determined per Sections 11.4.6 and 21.3 of ASCE 7-16. The ordinates for the site-specific design response spectrum are presented in Table 1 (Column 12).

The risk-targeted site-specific MCER and design response spectra, as well as the mapped CBC response spectrum, are shown on Figure 5 and tabulated in Table 1.

A summary of the site-specific seismic parameters, as detailed in Table 1, are presented below:

Site Class D SMS : 2.246 g

PGAM: 0.976g SM1 : 1.720 g

SDS : 1.497 g SD1 : 1.146 g

3065-I-02R.doc (11/23) 8

4.2.3 Liquefaction and Seismic Settlement

Soil liquefaction is a phenomenon in which saturated cohesionless soils undergo a temporary loss of strength during severe ground shaking and acquire a degree of mobility sufficient to permit ground deformation. In extreme cases, the soil particles can become suspended in groundwater, resulting in the soil deposit becoming mobile and fluid-like. Liquefaction is generally considered to occur primarily in loose to medium dense deposits of saturated cohesionless soils. Thus, three conditions are required for liquefaction to occur: (1) a cohesionless soil of loose to medium density; (2) a saturated condition; and (3) rapid large strain, cyclic loading, normally provided by earthquake motions.

The site is not located in a seismic Hazard Zone for liquefaction, as mapped by the State of California (Beverly Hills Quadrangle). Maps presented in the City and County of Los Angeles Seismic Safety Elements also locate the site outside of areas considered to be liquefiable (City of Los Angeles, 1996; County of Los Angeles, 1990). Excluding the site from a liquefaction hazard zone appears to be based primarily on the very stiff to hard, fine grained older alluvial deposits at the site.

Seismic ground subsidence, not related to liquefaction, occurs when loose, granular soils above the groundwater are densified during strong earthquake shaking. Due to the very stiff, fine grained, older alluvial materials beneath the site, the potential for seismic ground subsidence to adversely affect the site is considered to be low.

4.3 EARTHWORK

The earthwork anticipated at the project site will consist of removal of undocumented fills, excavations for new footings and interior utility lines, subgrade preparation, and the placement and compaction of fill.

4.3.1 Clearing

Prior to grading, the areas to be developed should be stripped of vegetation, pavements, and cleared of all debris. Buried obstructions, such as utilities and tree roots, should be removed. Although none were encountered, cesspools or septic systems exposed during construction should be removed in their entirety. The resulting excavation should be backfilled as recommended in the "Subgrade Preparation" and "Placement and Compaction of Fill" sections of this report. As an alternative, cesspools can be backfilled with a lean sand-cement slurry. Deleterious materials generated during the clearing operations should be removed from the site. At the conclusion of the clearing operations, a representative of the GPI should observe and accept the site prior to further grading.

4.3.2 Excavations

Excavations at this site will include removals of undocumented fill and disturbed and low-density natural soils, footing excavations, and trenching for proposed utility lines.

3065-I-02R.doc (11/23) 9

To provide uniform support for the planned building, prior to placement of fills or construction of the building, the existing fill and a portion of the upper natural soils within the proposed building pad should be removed and replaced as properly compacted fill.

For planning purposes, removals for the building pad should extend to a depth of 4 feet below existing grades or 2 feet below the base of foundations, whichever is deeper.

Deeper removals may be required if undocumented fills are observed to extend below a depth of 4 feet below existing grade during pad grading.

Removals below minor structures, such as free-standing walls and trash enclosures, should extend to a depth of 3 feet below existing grade or 1 foot below the base of the foundation, whichever is deeper. Within pavement and hardscape areas, removals should extend to a depth of 1 foot below the existing grade or proposed subgrade, whichever is deeper.

The actual depths of removals should be determined in the field by GPI personnel during grading. The soils exposed at the base of the overexcavation should be processed in place as described in the “Subgrade Preparation” section of this report.

The Project Surveyor should accurately stake the corners of the areas to be overexcavated in the field. Where space is available, the base of the excavations should extend laterally at least 5 feet beyond the building lines or edge of foundations, or a minimum distance equal to the depth of overexcavation/compaction below finish grade (i.e., a 1:1 projection below the top outside edge of footings), whichever is greater.

Building lines include the footprint of the building and other foundation supported improvements, such as canopies and attached site walls.

Excavation of the soils at the site should be readily achieved using conventional methods. The contractor should determine the best method for removal based on the subsurface conditions outlined herein.

Where not removed by the aforementioned excavations, existing utility trench backfill should be removed and replaced as properly compacted fill within the building pad. This is especially important for deeper fills associated with existing sewers and storm drains.

For planning purposes, removals over the utilities should extend to within 1-foot of the top of the pipe. For utilities that are 5 feet or shallower, the removal should extend laterally 1-foot beyond both sides of the pipe. For deeper utilities, the removals should include a zone defined by a 1:1 projection upward (and away from the pipe) from each side of the pipe. The actual limits of removal will be confirmed in the field. We recommend that known utilities be shown on the grading plan. Wet utilities left in-place outside building areas should be capped to reduce the potential for water to infiltrate into the building pad.

The upper soils at the site are expected to have a low caving potential when exposed in open cuts. Temporary construction excavations may be made vertically into the undisturbed natural soils without shoring to a depth of 5 feet below adjacent grade. For cuts up to 15 feet deep, the slopes should be properly shored or sloped back to at least 1:1 or flatter. For deeper cuts, while not anticipated, the slopes should be properly shored or sloped back to at least 1½:1 (horizontal to vertical) or flatter. The allowable slope inclinations are measured from the toe to the top of the cut. Even at these

3065-I-02R.doc (11/23) 10 inclinations, some raveling should be anticipated. The exposed slope face should be kept moist (but not saturated) during construction to reduce local sloughing. Surcharge loads should not be permitted within a horizontal distance equal to the height of cut from the top of the excavation or 5 feet from the top of the slopes, whichever is greater, unless the cut is properly shored. Excavations that extend below an imaginary plane inclined at 45 degrees below the edge of adjacent existing site facilities should be properly shored to maintain support of adjacent elements. Excavations and shoring systems should meet the minimum requirements given in the State of California Occupational Safety and Health Standards.

Deeper removals along property lines or adjacent to existing improvements will require shoring or slot cuts. Recommendations for shoring are provided in the “Lateral Earth Pressures” section of the report. Removals that will undermine existing adjacent pavements or hardscape may utilize “ABC” slot cuts to depths not greater than 8 feet.

Unsurcharged slot cuts up to 8 feet in height should not be wider than 6 feet and should be backfilled to finished grade prior to excavation of the adjacent four slots (two on each side of the excavated slot). We should be provided details of the building and excavation to provide final recommendations before making the excavations. A test slot should be performed prior to production slots to confirm the stability of the planned cuts.

4.3.3 Subgrade Preparation

After removals are complete and prior to placing fills or construction of the proposed structures, the subgrade soils should be scarified to a depth of 8 inches, moisture-conditioned, and compacted to dry densities equal to at least 90 percent of the maximum dry density as determined in accordance with ASTM D 1557.

4.3.4 Material for Fill

The existing site soils are, in general, suitable for use as compacted fill. However, the on-site clays and silts should not be used as retaining wall backfill or placed within 12 inches of the finished subgrade for floor slabs or pedestrian hardscape areas.

Imported fill material should be predominately granular (containing no more than 40 percent fines - portion passing No. 200 sieve) and non-expansive (Expansion Index of 20 or less) and not contain particles greater than 6 inches in size. GPI should be provided with a sample (at least 50 pounds) and notified of the location of soils proposed for import at least 72 hours in advance of importing. Each proposed import source should be sampled, tested and accepted for use prior to delivery of the soils to the site. Soils imported prior to acceptance by GPI may be rejected if not suitable.

If used as fill, open-graded gravel, such as pea gravel or crushed rock, should be placed in lifts of not more than 12 inches thick and densified with vibratory or impact compaction equipment. In addition, such materials should be separated from the adjacent soil with a suitable filter fabric, such as Mirafi 140N or equivalent.

3065-I-02R.doc (11/23) 11

4.3.5 Placement and Compaction of Fills

Fill soils should be placed in horizontal lifts, moisture-conditioned, and mechanically compacted to at least 90 percent of the maximum dry density, in accordance with ASTM D-1557. Imported sands and aggregate base material should be compacted to at least 95 percent of the maximum dry density, in accordance with ASTM D-1557.

The moisture content of clays and silts should be between 1 to 3 percent over the optimum moisture content, and sands should be between 0 and 2 percent over the optimum moisture content to readily achieve the required degree of compaction. The on-site clays and silts near the existing surface are generally near optimum moisture content, however some moisture-conditioning (drying, wetting and mixing) during grading may be required.

4.3.6 Shrinkage and Subsidence

Shrinkage is the loss of soil volume caused by compaction of fills to a higher density than before grading. Subsidence is the settlement of in-place subgrade soils caused by loads generated by large earthmoving equipment. For earthwork estimating purposes, an average shrinkage value of 5 to 10 percent and subsidence of 0.1 feet may be assumed for the surficial soils for earthwork volume estimating purposes. Actual shrinkage and subsidence will depend on the types of earthwork equipment used and can be determined during grading.

4.3.7 Observation and Testing

A representative of GPI should observe excavation bottoms, subgrade preparation, and fill placement activities. Sufficient in-place field density tests should be performed during fill placement and in-place compaction to evaluate the overall compaction of the soils.

Soils that do not meet minimum compaction requirements should be reworked and tested prior to placement of any additional fill.

4.3.8 Trench/Wall Backfill

Utility trench backfill should be mechanically compacted in lifts. Wall backfill should consist of imported sandy soils. Lift thickness should not exceed the values given in the "Compacted Fill" section of this report. Jetting or flooding of backfill materials should not be permitted. A representative of GPI should observe and test trench and wall backfill as they are placed.

In backfill areas where mechanical compaction of soil backfill is impractical due to space constraints, sand-cement slurry may be substituted for compacted backfill. The slurry should contain at least 1½ sack of cement per cubic yard and have a maximum slump of 5 inches. Within building areas, the slurry should contain two sacks of cement per cubic yard.

3065-I-02R.doc (11/23) 12

4.4 FOUNDATIONS

4.4.1 General

As discussed previously, the proposed structures can be supported on conventional spread footings founded in properly compacted fill.

4.4.2 Allowable Bearing Pressures

Based on the shear strength and elastic settlement characteristics of the natural site soils and properly compacted fill, a static allowable net bearing pressure of up to 3,000 pounds per square foot (psf) may be used for the structures. These bearing pressures are for dead-plus-live loads, and may be increased one-third for short-term, transient, wind and seismic loading. The actual bearing pressure used may be less, such that economics and structural loads will determine the minimum width for footings as discussed below. The maximum edge pressures induced by eccentric loading or overturning moments should not be allowed to exceed these recommended values.

4.4.3 Minimum Footing Width and Embedment

The following minimum footing widths and embedments are recommended for the corresponding allowable bearing pressure.

STATIC BEARING

PRESSURE

(psf)

MINIMUM FOOTING

WIDTH

(inches)

MINIMUM FOOTING*

EMBEDMENT

(inches) 3,000 48 24 2,500 36 24 2,000 24 24 1,500 18 18

* Refers to minimum depth below lowest adjacent grade.

A minimum footing width of 18 inches should be used even if the actual bearing pressure is less than 1,500 psf as shown above.

4.4.4 Estimated Structural Settlements

Total static settlement of isolated pad or continuous wall footings (up to 100 kips for columns and 8 kips per lineal foot for walls) is expected to be on the order of ¾-inch or less. Differential static settlement along a 60-foot span expected to be on the order of ½-inch or less.

The above estimates are based on the assumption that the recommended earthwork will be performed and that the footings will be sized in accordance with our recommendations.

3065-I-02R.doc (11/23) 13

4.4.5 Lateral Load Resistance

Soil resistance to lateral loads will be provided by a combination of frictional resistance between the bottom of footings and underlying soils and by passive soil pressures acting against the embedded sides of the footings. For frictional resistance, a coefficient of friction of 0.30 (FS=1.5) may be used for design. In addition, an allowable lateral bearing pressure equal to an equivalent fluid weight of 275 pounds per cubic foot may be used, provided the footings are poured tight against compacted fill soils. These values may be used in combination without reduction.

4.4.6 Light Standards and Poles

We understand that fences and light standards are planned as part of the proposed project. The new fences, light standards, and similar structures may be supported on drilled pile foundations established in the existing fill soils or natural materials. The design of such piles is typically governed by lateral loading conditions. Soil resistance to lateral loads can be provided by the piles. For design by the simplified pole formula presented in Section 1807A.3.2.1 of the 2022 CBC, a unit passive resistance of 275 pounds per square foot per foot (to a maximum of 2,500 pounds per square foot) may be used for the piles with level ground in lieu of the presumptive lateral bearing values presented in Table 1806A.2. As stated in the code, the above passive resistance may be doubled (550 pounds per square foot per foot, up to a maximum of 5,000 pounds per square foot) for isolated piles as determined by the Project Structural Engineer. This value incorporates the allowable increase stated in Section 1806A.3.4 of the code for single poles that can tolerate a ½-inch of deflection under short-term loads.

We recommend the upper 1-foot of the subgrade soils be ignored in determining the required depth of embedment for lateral capacity to allow for surface disturbance adjacent to the pile. We should note that Section 1807A.3.2.1 of the 2022 CBC pertains to non-constrained piles (i.e. free head conditions). For constrained piles (i.e. fixed head conditions), the formula presented in Section 1807A.3.2.2 should be used.

A pile designed for adequate embedment to resist the anticipated lateral loads for minor structures such as fences and light standards should have adequate axial capacity to support the anticipated vertical loads. The net allowable vertical compressive capacity can be conservatively calculated based on a unit side friction of 150 pounds per square foot, neglecting end-bearing contribution. Again, we recommend that the upper 1-foot of the subgrade soils be ignored in determining the required depth of embedment for axial capacity to allow for future surface disturbance adjacent to the pile.

4.4.7 Foundation Concrete

Laboratory testing by HDR (Appendix B) on a selected sample indicates that the near surface soils exhibit a soluble sulfate content of 57mg/kg. For the 2022 CBC, foundation concrete should conform to the requirements outlined in ACI 318, Section 4.3 for negligible levels of soluble sulfate exposure from the on-site soils, (Category S0).

Chloride levels in the sample of the upper soils tested were found to be 25 mg/kg, which is considered to be low (Category C1).

3065-I-02R.doc (11/23) 14

4.4.8 Footing Excavation Observation

Prior to placement of concrete and steel, a representative of GPI should observe and approve footing excavations.

4.5 BUILDING FLOOR SLABS

Slab-on-grade floors should be supported on at least 1 foot of non-expansive (Expansion Index of 20 or less), compacted soils as discussed in the “Placement and Compaction of Fill” section. In general, the on-site soils will not meet this requirement.

As such, import soils will be required.

A vapor/moisture retarder should be placed under slabs that are to be covered with moisture-sensitive floor coverings (parquet, vinyl tile, etc.) or will be storing moisture sensitive supplies. Currently, common practice is to use a 15 mil polyolefin product such as Stego Wrap for this purpose. Whether to place the concrete slab directly on the vapor barrier or place a clean sand layer between the slab and vapor barrier is a decision for the Project Architect, as it is not a geotechnical issue. If covered by sand, the sand layer should be about 2 inches thick and contain less than 5 percent by weight passing the No. 200 sieve. Based on our explorations and laboratory testing, the soils at the site are not suitable for this purpose. The function of the sand layer is to protect the vapor retarder during construction and to aid in the uniform curing of the concrete. This layer should be nominally compacted using light equipment. The sand placed over the vapor retarder should only be slightly moist. If the sand gets wet (for example as a result of rainfall or excessive moistening) it must be allowed to dry prior to placing concrete.

Care should be taken to avoid infiltration of water into the sand layer after placement of the concrete slab, such as at slab cut-outs and other exposures. A sand layer is not required beneath the vapor retarder, but we take no exception if one is provided.

It should be noted that the material used as a vapor retarder is only one of several factors affecting the prevention of moisture accumulation under floor coverings. Other factors include maintaining a low water to cement ratio for the concrete used for the floor slab, effective sealing of joints and edges (particularly at pipe penetrations), as well as excess moisture in the concrete. The manufacturer of the floor coverings should be consulted for establishing acceptable criteria for the condition of floor surface prior to placing moisture-sensitive floor coverings.

4.6 LATERAL EARTH PRESSURES

The following recommendations are provided for retaining walls that do not extend more than 10 feet in height. We recommend that conventionally constructed walls be backfilled with sandy (granular) soils, which are not anticipated to be readily available on-site.

Active earth pressures can be used for designing walls that can yield at least ½-inch laterally in 10 feet of wall height under the imposed loads. For drained level backfill comprised of non-expansive granular soils (no more than 40 percent passing No. 200 U.S. standard sieve), the magnitude of active pressures are equivalent to the pressures imposed by a fluid weighing 35 pounds per cubic foot (pcf). This pressure may also be

3065-I-02R.doc (11/23) 15 used for the design of temporary excavation support. For the natural on-site soils, the magnitude of active pressures are equivalent to the pressures imposed by a fluid weighing 56 pounds per cubic foot (pcf) for drained level backfill.

At-rest pressures should be used for restrained walls that remain rigid enough to be essentially non-yielding, such as basement walls. At-rest pressures for drained non-expansive granular soils are equivalent to the pressures imposed by a fluid weighing 55 pcf. At-rest pressures for on-site natural drained soils are equivalent to the pressures imposed by a fluid weighing 78 pcf.

If it is desired to account for seismic loads, an additional lateral earth pressure equal to 22 pcf (equivalent fluid pressure distribution) should be added to the above active pressure. If the wall is designed using the above at-rest pressures, the lateral earth pressure combined with a seismic load should be limited to 57 or 78 pcf (equivalent fluid pressure distribution) for granular non-expansive or on-site silt/clay soils, respectively.

Walls subject to surcharge loads should be designed for an additional uniform lateral pressure equal to one-third and one-half the anticipated surcharge pressure for unrestrained and restrained walls, respectively. The wall backfill should be well-drained to relieve possible hydrostatic pressure or designed to withstand these pressures.

The wall backfill for conventional walls should be well-drained to relieve possible hydrostatic pressure or designed to withstand these pressures. A drain consisting of perforated pipe and gravel wrapped in filter fabric should be used. One cubic foot of rock should be used for each lineal foot of pipe. The fabric (non-woven filter fabric, Mirafi 140N or equivalent) should be lapped at the top.

The Structural Engineer should specify the use of select, granular wall backfill on the plans for retaining walls that are to be conventionally backfilled. Wall footings should be designed as discussed in the "Foundations" section.

4.7 CORROSION

Soil corrosivity testing was performed by HDR under subcontract to GPI. The corrosivity test results are presented in Appendix B. The on-site soils should be considered moderately corrosive to buried metals. If corrosion consultation is required, a corrosion engineer such as HDR should be consulted.

4.8 EXTERIOR CONCRETE FLATWORK (PEDESTRIAN HARDSCAPE)

Exterior concrete pads and pedestrian hardscape should be supported on a 12-inch thick layer of non-expansive granular soil. This includes exterior sidewalks, stamped concrete, non-traffic pavement, and pavers. Prior to placement of concrete, the subgrade should be prepared as recommended in the "Subgrade Preparation" section of this report.

We recommend the Project Civil Engineer design the concrete hardscape and sidewalks, including determination of thickness and reinforcing. For exterior flatwork, hardscape, and sidewalks, we recommend a minimum slab thickness of 4 inches with

3065-I-02R.doc (11/23) 16 minimum slab reinforcement of No. 3 rebar placed at 18 inches on-center, in both directions. Control joints to direct shrinkage cracking in exterior slabs and sidewalks should be provided at maximum spacing of 8 and 6 feet on center in two directions, respectively. These recommendations should be considered as minimums based on the geotechnical site conditions, and the Project Civil Engineer should confirm if more stringent recommendations are needed for other purposes.

4.9 PAVED AREAS

A test on the upper soils resulted in an R-value of 9. To account for variability of the onsite soils, we have used an R-value of 5 for our calculations. The following pavement sections are recommended for planning purposes only. These recommendations assume that the pavement subgrades will consist of existing near surface soils. The following pavement sections are recommended for typical traffic uses:

ASPHALT CONCRETE PAVEMENT ON UNTREATED SUBGRADE

PAVEMENT AREA

TRAFFIC INDEX

SECTION THICKNESS (inches)

ASPHALT

CONCRETE

AGGREGATE

BASE COURSE

Auto Parking 4 3 7

Auto Drives 5 3.5 10

Truck Traffic 6 4 12

PORTLAND CEMENT CONCRETE PAVEMENT ON 4-INCHES OF AGGREGATE BASE OVER SUBGRADE

PAVEMENT AREA

TRAFFIC

INDEX

SECTION THICKNESS (inches) f’c = 3,000 psi

PCC

f’c = 3,500 psi

PCC

f’c = 4,000 psi

PCC

Auto Parking/Drives 5 7

6.5 6

Truck Traffic 6.0 8 7.5 7

We recommend portland cement concrete (PCC) pavement be underlain by 4 inches of aggregate base. Besides improving overall support, the aggregate base will serve to maintain the moisture content of the properly compacted clays and provide a working surface prior to the placement of the PCC.

The pavement subgrade underlying the aggregate base should be properly prepared and compacted in accordance with the recommendations outlined under "Subgrade Preparation". The subgrade soils should not be allowed to dry-out prior to covering with the aggregate base or pavement, and a representative from GPI should test the subgrade moisture content immediately prior to covering. If the soils are allowed to dry-out, additional processing and moisture conditioning will be required to achieve the moisture contents discussed previously in the Placement and Compaction of Fills section of this report.

The pavement base course should be compacted to at least 95 percent of the maximum dry density (ASTM D1557). Aggregate base should conform to the requirements of Section 26 of the California Department of Transportation Standard Specifications for

3065-I-02R.doc (11/23) 17

Class II aggregate base (three-quarter inch maximum) or Section 200-2 of the Standard Specifications for Public Works Construction (Green Book) for untreated base materials (except processed miscellaneous base).

The above recommendations assume that the base course and compacted subgrade will be properly drained. The design of paved areas should incorporate measures to prevent moisture build-up within the base course which can otherwise lead to premature pavement failure. For example, curbing adjacent to landscaped areas should be deep enough to act as a barrier to infiltration of irrigation water into the adjacent base course.

4.10 STORM WATER INFILTRATION

Current regulations require that storm water be infiltrated in the site soils of new developments when possible. The soil types present at the site control the ability of water to infiltrate into the subgrade. Based upon our subsurface investigation and laboratory testing, the subsurface soils underlying the site consist of predominately very stiff to hard clays and silts with partial cementation (Older Alluvium), which are typically not adequate to accept infiltration. Based on these soil types, it is our opinion that subsurface infiltration of storm water is not likely to be feasible.

If required by the reviewing agency, we can confirm the inadequacy of the soils to properly infiltrate storm water by performing percolation tests to establish infiltration rates of the soils. If required, percolation testing should be performed in accordance with the guidelines of the County of Los Angeles (COLA, 2021).

4.11 GEOTECHNICAL OBSERVATION AND TESTING

We recommend that a representative of GPI observe earthwork during construction to confirm that the recommendations provided in our report are applicable during construction. The earthwork activities include grading, compaction of fills, subgrade preparation, pavement construction and foundation excavations. If conditions are different than expected, we should be afforded the opportunity to provide an alternate recommendation based on the actual conditions encountered.

3065-I-02R.doc (11/23) 18

5.0 LIMITATIONS

The report, exploration logs, and other materials resulting from GPI's efforts were prepared exclusively for use by Spees LLC and their consultants in designing the proposed development. The report is not intended to be suitable for reuse on extensions or modifications of the project or for use on any project other than the currently proposed development as it may not contain sufficient or appropriate information for such uses. If this report or portions of this report are provided to contractors or included in specifications, it should be understood that they are provided for information only.

Soil deposits may vary in type, strength, and many other important properties between points of exploration due to non-uniformity of the geologic formations or to man-made cut and fill operations. While we cannot evaluate the consistency of the properties of materials in areas not explored, the conclusions drawn in this report are based on the assumption that the data obtained in the field and laboratory are reasonably representative of field conditions and are conducive to interpolation and extrapolation.

Furthermore, our recommendations were developed with the assumption that a proper level of field observation and construction review will be provided during grading, excavation, and foundation construction by GPI. If field conditions during construction appear to be different than is indicated in this report, we should be notified immediately so that we may assess the impact of such conditions on our recommendations. If construction phase services are performed by others they must accept full responsibility for all geotechnical aspects of the project including this report.

Our investigation and evaluations were performed using generally accepted engineering approaches and principles available at this time and the degree of care and skill ordinarily exercised under similar circumstances by reputable Geotechnical Engineers practicing in this area. No other representation, either expressed or implied, is included or intended in our report.

Respectfully submitted, Geotechnical Professionals Inc.

Patrick I.F. McGervey, P.E. Donald A. Cords, G.E Project Engineer Principal

Thomas G. Hill, C.E.G.

Consulting Geologist

3065-I-02R.doc (11/23) 19

REFERENCES

American Society of Civil Engineers (2017), “Minimum Design Loads and Associated Criteria for Buildings and Other Structures,” ASCE/SEI 7-16.

California Department of Conservation, Division of Mines and Geology (1997), “Special Publications 117: Guidelines for Evaluating and Mitigating Seismic Hazards in California.”

California Geological Survey (2018), Earthquake Zones of Required Investigation:

Beverly Hills Quadrangle, published January 11, 2018.

California Department of Water Resources, Water Data Library, http://www.water.ca.gov/waterdatalibrary/

California Geological Survey, 1998, Seismic Hazard Zone Report for the Beverly Hills 7.5-minute Quadrangle, Los Angeles County, California, Seismic Hazard Zone Report 023.

California Office of Statewide Health Planning and Development (OSHPD), Seismic Design Maps Website, https://seismicmaps.org/

City of Los Angeles, 1996, Safety Element of the Los Angeles City General Plan, November 26, 1996.

County of Los Angeles, Department of Public Works, Geotechnical and Materials Engineering Division, 2017, “Administrative Manual: Guidelines for Geotechnical Investigation and Reporting, Low Impact Development Stormwater Infiltration,” GS299.2, dated June 30, 2021

County of Los Angeles, 1990, Safety Element of the Los Angeles County General Plan, December 6, 1990.

California Department of Conservation, Division of Mines and Geology (1997), “Special Publications 117: Guidelines for Evaluating and Mitigating Seismic Hazards in California.”

California Office of Statewide Health Planning and Development (OSHPD), Seismic Design Maps Website, https://seismicmaps.org/

Historical Aerials, Aerial Photography from the Past and Present, www.historicaerials.com, National Environmental Title Research, LLC

U.S. Department of Veterans Affairs, Veterans Administration Handbook 18-8, Seismic Design Requirements, November 1,…