W50S8X20B0001-0002_Attachment_5_Geotechnical_Report.pdf

Geotechnical Report California Air National Guard 129th Rescue Wing Relocation Project

Moffett Federal Airfield

Mountain View, CA March 17, 2017

California Air National Guard 129th Rescue Wing Relocation Project

March 17, 2017 | i

Kimberly I. Brown, Project Engineer

Mark H. Stanley, P.E., G.E., Geotechnical Engineer

No. 2397 Exp. 9/30/2018 Geotechnical

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Contents

1 Introduction

1.1 Project Description

1.2 Scope of Services

1.3 Coordinate System and Units

1.4 Code and Standards

2 Geotechnical Exploration

2.1 Existing Subsurface Explorations

2.2 Project Subsurface Explorations

2.2.1 Exploration Preparation

2.2.2 Explorations

2.3 Project Laboratory Testing

3 Geologic Setting

3.1.1 Regional Geology

3.1.2 Site Geology

3.1.3 Regional Seismicity

3.2 Geologic Hazards

3.2.1 Fault Rupture

3.2.2 Liquefaction

3.2.3 Seiches and Tsunamis

3.3 Flooding

4 Site Conditions

4.1 Surface Conditions

4.2 Subsurface Conditions

4.3 Groundwater

5 Discussions and Conclusions

5.1 General

5.1.1 Liquefaction

5.1.2 Foundation Support

5.1.3 Expansive Potential

5.2 PV# Project Specific Discussions and Conclusions

5.2.1 PV2 – Aircraft Engine Inspection and Maintenance Shop

5.2.2 PV3 – Squadron Operations and PV6 – Small Air Terminal & Cargo

Deployment Staging Area

5.2.3 PV4 – Fuel Cell Corrosion Control Hangar, Aircraft Wash Rack, & Utility

Storage and PV7 – Aerospace Support Equipment Shop & Storage Yard

5.2.4 PV5 – Munitions Storage Area

5.2.5 PV9 – Pararescue Storage Facility

5.2.6 PV13 – Cryogenics Storage & Canopy

5.2.7 PV21 – North and Central Parking Expansion

5.2.8 PV23 – North and Central Parking Expansion

6 Recommendations

6.1 Seismic Design Criteria

6.2 Earthwork

6.2.1 Stripping and Demolition

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6.2.2 Densification of Potentially Liquefiable Soils

6.2.3 Subgrade Preparation

6.2.4 Engineered Fill Materials

6.2.5 Fill Placement and Compaction

6.3 Temporary Excavations

6.3.1 Excavations

6.3.2 Pipe Backfill

6.3.3 Trench Backfill

6.4 Shallow Foundation

6.4.1 Allowable Bearing Capacity

6.4.2 Lateral Resistance

6.5 Mat Foundation

6.6 Slab-On-Grades

6.7 Deep Foundation Construction

6.7.1 Axial Capacity

6.7.2 Group Effects

6.7.3 Construction Considerations

6.8 Pavements

6.8.1 Pavement Design

6.8.2 Flexible Pavement

6.8.3 Rigid Pavement

6.8.4 CBR Testing

6.8.5 Construction Considerations

6.9 Additional Geotechnical Services

7 Limitations

8 References

Tables

Table 1-1-1 Proposed Facilities Table 2-1 Summary of Explorations Table 3-1. Nearest Active Faults Table 4-1. Groundwater Elevations Table 5-1 PV2 Summary of Explorations Table 5-2 Summary of PV2 Bearing Capacity and Settlement Analyses Table 5-3 PV2 Calculated Liquefaction Settlement CPT HDR-3 Table 5-4 PV3/6 Summary of Explorations Table 5-5 Summary of PV3/6 Bearing Capacity and Settlement Analyses Table 5-6 PV3/6 Liquefaction Table 5-7 PV4/7 Summary of Explorations Table 5-8 Summary of PV4/7 Bearing Capacity and Settlement Analyses Table 5-9 PV4 Soil Parameters for Lateral Pile Capacity Table 5-10 PV4/7 Liquefaction Table 5-11 PV5 Summary of Explorations Table 5-12 PV5 Structural Loads – Administration and Inert Storage Buildings Table 5-13 PV5 Structural Loads – Maintenance and Inspection and ECM

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Table 5-14 PV5 Soil Parameters for Lateral Pile Capacity Table 5-15 PV5 Liquefaction Table 5-16 PV9 Summary of Explorations Table 5-17 PV13 Summary of Explorations Table 5-18 PV13 Structural Loads Table 6-1 Seismic Design Parameters Table 6-2 Flexible Pavement Sections Table 6-3 Flexible Pavement Design Sections with Chemically Treated Base Table 6-4 Depth of Compaction for Select per ESAL and Percent Compaction (CBR = 20) Table 6-5 Rigid Pavement Design Sections Table 6-6 Summary of CBR Testing

Figures

Figure 1-1 - Overall Project Site Plan

Figure 1-2 - Final FEA Plan

Figure 2-1 - Boring Location Map North

Figure 2-2 - Boring Location Map Central

Figure 2-3. Boring Location Map South

Figure 3-1 - Geologic Map

Figure 3-2 - Regional Geology Map

Figure 3-3 - Seismic Hazards Map

Figure 3-4 - Tsunami Inundation Map

Figure 3-5 - FEMA Flood Map

Figure 4-1 - Cross-Section A-A

Figure 4-2 - Cross-Section B-B

Figure 4-3 - Cross Section C-C

Figure 4-4 - Cross Section D-D

Figure 4-5 - Cross Section E-E

Figure 5-1 - Lateral Deflection Vs. Depth 18-inch Auger Cast Pile

Figure 5-2 - Bending Moment Vs. Depth 18-inch Auger Cast Pile

Figure 5-3 - Shear Vs. Depth 18-inch Auger Cast Pile

Figure 5-4 - Allowable Axial Capacity Vs. Depth 18-inch Auger Cast Pile

Figure 5-5 - Lateral Deflection Vs. Depth 18-inch Auger Cast Pile

Figure 5-6 - Bending Moment Vs. Depth 18-inch Auger Cast Pile

Figure 5-7 - Shear Vs. Depth 18-inch Auger Cast Pile

Exhibits

Exhibit 4-1. General Site Conditions Exhibit 5-1. ’ of Cohesive Soils Based on PI Exhibit 5-2. Effective Friction Angle of Sand Based on SPT Resistance Exhibit 5-3. PV2 Floor Plan Exhibit 5-4. PV3/6 Floor Plan iv | March 17, 2017

Exhibit 5-5. PV4/7 Floor Plan Exhibit 5-6. PV5 Layout Exhibit 5-7. PV5 Administration Building Floor Plan Exhibit 5-8. PV5 Maintenance and Inspection Building Floor Plan Exhibit 5-9. PV5 Inert Storage Floor Plan Exhibit 5-10. PV8 Refueler Parking Area Floor Plan Exhibit 5-11. PV9 Floor Plan Exhibit 5-12. PV13 Floor Plan

Appendices

Appendix A. Historical Explorations ........................................................................................................... A-1

Appendix B. Project Boring Logs ............................................................................................................... B-1

Appendix C. Project CPTs ........................................................................................................................ C-1

Appendix D. Project Lab Testing .............................................................................................................. D-1

Appendix E. Liquefaction Analysis ............................................................................................................. E-1

Appendix F. Prestressed Concrete Pile Allowable Axial Capacity Calculations ........................................ F-1

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1 Introduction

1.1 Project Description

HDR Engineering, Inc. (HDR) is assisting Google-Planetary Ventures (Google/PV) in evaluating and designing the proposed facilities for the California Air National Guard (CAANG) 129th Rescue Wing Relocation Project (Project). Currently, the CAANG 129th Rescue Wing operations are spread among several locations within Moffett Federal Airfield (Moffett Field), including those areas that will be transferred to Google/PV as part of the Facility Exchange Agreement (FEA). The Project includes relocating all functions of the CAANG 129th Rescue Wing within the boundaries of the cantonment area (site).

Figure 1-1 – Overall Project Site Plan shows the location of the site.

The Project includes design of the 11 facilities and demolition of 10 structures at the site.

Table 1-1 lists the Planetary Ventures project identification number (PV#), program name, description, and location. We obtained the information included in Table 1-1 from the 30 percent Basis of Design reports (HDR, 2016a, 2016b, and 2016c). Figure 1-2 – Final FEA Plan shows the locations of the proposed PV facilities.

The discussions presented herein reflect the project understanding at the 30 design phase as documented in the 30 percent design submittals (HDR 2016a, b and c).

Changes in the project during subsequent design phases could necessitate supplemental geotechnical evaluations which could change conclusions and modify recommendation that are contained in this report. Any changes in the geotechnical conclusions recommendations would be documented in separate technical memoranda, as required, that will be issued as supplement to this report.

Table 1-1-1 Proposed Facilities

PV # Program Name Building Description Location

PV2 Aircraft Engine Inspection and Maintenance Shop

30,930 gross square feet one-story building constructed of CMU material

Adjacent to Aircraft Hangar 662

PV3 Squadron Operations 25,600 gross square feet two-story building constructed of CMU for both stories (subject to change) and connected to PV6 with expansion joint

North of Pararescue Operations Building 663 and adjacent to proposed PV6

PV4 Fuel Cell/Corrosion Control Hangar, Aircraft Wash Rack, and Utility Storage

46,500 gross square feet two-story aircraft hanger constructed of steel surrounded by a one-story building on the north, east, and south sides constructed of CMU material

Northwest of Aircraft Hangar 662 and proposed PV2. Adjacent to PV7

PV5 Munitions Storage Area Munitions administration building

– 3,900 gross square feet one-story building constructed of CMU material

South of Building 679

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Table 1-1-1 Proposed Facilities

PV # Program Name Building Description Location

Maintenance inspection building

- one-story building constructed of CIP walls in-filled with soil

Inert storage building – 1,200 gross square feet one-story building constructed of CMU material

Earth covered magazine buildings – 11 structures at various sizes constructed at grade with CMU material and covered with 2 feet of fill

PV6 Small Air Terminal and Cargo Deployment Staging Area

12,900 gross square feet two-story building constructed of CMU for both stories (subject to change) and connected to PV3 with expansion joint

North of Pararescue Operations Building 663 and adjacent to proposed PV3

PV7 Aerospace Support Equipment (ASE) Shop and Storage Yard

ASE Shop included in PV4 square feet and 8,100 gross square feet ASE storage yard

Northwest of Aircraft Hangar 662 and proposed PV2. Adjacent to PV4

PV8 Refueler Parking Area Concrete pavement North of Buildings 654, 655, and 669 and adjacent to proposed PV13

Petroleum Operations Building

Included in PV4 Located in PV4

PV9 Pararescue Storage Facility

Asphalt concrete pavement Southeast of Pararescue Operations Building 663

PV13 Cryogenics Storage and Canopy

Concrete pavement with steel canopy structure

Northwest of Buildings 654, 655, and 669 and adjacent to proposed PV8

PV21 North Parking Expansion Asphalt concrete pavement Northwest and west of Building 653

Central Parking Expansion Asphalt concrete pavement South of Building 650

PV23 Site and Infrastructure Improvements

Asphalt concrete pavement (Jagels Road)

West of Building 653

PVX Demolition of Buildings 654-661 and 669

N/A West of Building 653

1.2 Scope of Services

The purpose of this report is to document our review of existing geotechnical data, our subsurface exploration, laboratory testing program, and geotechnical analyses, and provide geotechnical design recommendations for the proposed Project. Our scope of work included the following tasks:

Compiling and reviewing available existing geologic and geotechnical data for the project area

Preforming a site reconnaissance and marking the site for location of existing underground utilities near exploration locations

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Drilling 32 borings

Advancing 6 cone penetration tests (CPTs)

Geotechnical laboratory testing

Geologic site characterization

Geologic hazards evaluation

Foundation type, settlement and bearing capacity evaluations

Flexible and rigid pavement design

Development of geotechnical design and construction recommendations for:

o Site preparation and grading o Foundations o Slabs-on-grade o Seismic design parameters o Pavement

Preparing this geotechnical report.

1.3 Coordinate System and Units

The vertical datum for this work is the North American Vertical Datum of 1988 (NAVD88) and the horizontal datum is the North American Datum of 1983 (NAD83). We used English units for this Project.

1.4 Code and Standards

Note the requirements defined in the Unified Facilities Criteria (UFC) and Air National Guard Engineering Technical Letters will take precedent over the California Codes.

Referenced dates are not listed here, but in accordance with UFC 1-200-01 §1-8.

UFC DoD Building Code (General Building Requirements) (UFC, 2016a)

UFC 3-220-01 Geotechnical Engineering (UFC, 2012)

UFC 3-250-01 Pavement Design for Roads and Parking Areas (UFC, 2016b)

UFC 3-310-04 Seismic Design of Buildings (UFC, 2013)

UFC 3-320-06A Concrete Floor Slabs on Grade Subjected to Heavy Loads (UFC, 2005)

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2 Geotechnical Exploration

2.1 Existing Subsurface Explorations

Prior to conducting the field exploration and laboratory testing, we reviewed the following design plans and geotechnical reports prepared for the site:

California Air National Guard - NAS Moffett Field, Relocation to Moffett Field Design Plans prepared by Reid & Tarics, Associates in 1977 which included borings EB-1 through EB-16 to depths ranging from 5 to 30 feet.

Concrete Treatment Pad, Naval Air Station Moffett Field, Moffett Field, CA design plans prepared by James M. Montgomery Consulting Engineers, Inc. in 1991 which included borings BPSB-1 through BPSB-3 to depths ranging from 15 to 40 feet.

Geotechnical Investigation Report, California Air National Guard, Moffett Federal Airfield, Mountain View, CA prepared by Parikh Consultants, Inc. in 2010 for the proposed main gate facility which included borings B-1 through B-11 to depths ranging from 5 to 15 feet.

Final Geotechnical Data Report, Pararescue Training Facility, Moffett Federal Airfield, Mountain View, CA prepared by AGS in 2011 which included boring B-1 through B-3 to depths ranging from 46.5 to 101.5 feet, CPTs CPT-1 through CPT-3 to depths ranging from 70 to 100 feet, and percolation test holes PH-1 and PH-2.

Geotechnical and Geohazard Investigation, Capabilities Training Simulator Project, Moffett Federal Airfield, Mountain View, CA prepared by Cleary Consultants, Inc. in 2012 which included borings EB-1 through EB-3 to depths ranging from 25 to 46.5 feet.

Geotechnical Investigation Report, Vehicle Maintenance Facility, California Air National Guard, Moffett Federal Air Field, Mountain View, CA prepared by Parikh Consultants, Inc. in 2014 which included borings B-1 through B-4 to depths ranging from 30 to 44.5 feet.

We considered the locations and depths of existing exploration data when planning our subsurface investigation. The approximate locations of the previous explorations are shown on Figures 2-1 through 2-3 – Boring Location Maps and exploration logs are included in Appendix A.

2.2 Project Subsurface Explorations

2.2.1 Exploration Preparation

HDR developed exploration and heath and safety work plans prior to mobilizing to the site. The work plan included the location, depth of explorations and type of drilling method/equipment to be used to advance the boring. The field exploration program was developed by considering the historical explorations and the Final FEA Plan shown in Figure 1-2.

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As required by the Santa Clara Valley Water District a well (drilling) permit was obtained for the explorations deeper than 45 feet. Also, as required by NASA, a Safety Clearance Permit was obtained from the CAANG Civil Engineer Squadron. The proposed exploration locations were marked and Underground Service Alert was contacted to check for the presence of underground utilities in the public right-of-way. Cruz Brothers Locators, a private utility locator, was also retained to locate and mark the locations of detected underground utilities near the proposed exploration locations.

2.2.2 Explorations

Summary of Explorations

Our field investigation consisted of advancing a total of 6 cone penetration tests (CPTs) to depths of 100 feet, a total of 6 rotary wash borings to depths of 50 and 100 feet and 26 hollow stem auger borings to depths between 10 and 25 feet. The CPTs were performed by Gregg In-situ of Martinez California and the borings were drilled by Pitcher Drilling Company of East Palo Alto, California.

Figures 2-1 through 2-3 show the approximate locations of the borings. The locations of the explorations were determined by measuring the distance from existing site features and are accurate only to the degree implied by the method used. Coordinates provided were derived from Autocad base drawings of the site. The CPT soundings and boring logs are included in Appendix B and C, respectively. Details of the exploration program are provided below.

Table 2-1 Summary of Explorations

PV #

Exploration

Number Northing Easting

Surface Elevation

(feet) Depth (feet) Exploration

Type

PV2 HDR-1 1,976,344.02 6,114,436.37 17.6 26.5 Boring

HDR-2 1,976,217.29 6,114,514.97 19.2 26.5 Boring

HDR-3 1,976,173.34 6,114,419.84 19.5 50.4 CPT

PV3 HDR-4 1,975,224.15 6,114,196.04 21.8 36.5 Boring (RW)

HDR-5 1,975,149.64 6,114,298.10 23.2 36.5 Boring (RW)

HDR-6 1,975,284.38 6,114,347.12 22.8 50.4 CPT

PV4 HDR-7 1,976,660.18 6,114,218.07 16.7 51.5 Boring (RW)

HDR-8 1,976,732.26 6,114,324.95 15.2 100.4 CPT

HDR-9 1,976,527.23 6,114,428.89 16.9 101.5 Boring (RW)

HDR-10 1,976,489.78 6,114,245.92 17.1 50.4 CPT

HDR-31 1,976,604.41 6,114,226.03 17.0 16.5 Boring

HDR-32 1,976,628.96 6,114,270.81 15.9 16.5 Boring

HDR-33 1,976,612.96 6,114,321.38 15.2 16.5 Boring

HDR-34 1,976,595.02 6,114,366.27 15.2 16.5 Boring

HDR-35 1,976,534.22 6,114,373.33 16.2 16.5 Boring

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Table 2-1 Summary of Explorations

PV #

Exploration

Number Northing Easting

Surface Elevation

(feet) Depth (feet) Exploration

Type

HDR-36 1,976,534.51 6,114,355.59 16.9 16.5 Boring

HDR-37 1,976,496.90 6,114,243.62 17.3 16.5 Boring

PV5 HDR-11 1,973,615.48 6,114,707.79 30.0 50.4 CPT

HDR-12 1,973,315.61 6,114,735.13 30.8 25 Boring

HDR-27

1,973,473.97 6,114,701.42

30.4

16.5 Boring

HDR-39

1,973,065.66 6,114,741.51

32.1

PV6 HDR-13 1,975,263.14 6,114,408.90 22.9 26.5 Boring

HDR-14 1,975,290.55 6,114,525.54 22.2 26.5 Boring

HDR-15 1,975,353.44 6,114,391.82 21.3 26.5 Boring (RW)

PV7 HDR-16 1,976,355.60 6,114,346.99 17.7 50.4 CPT

PV8 HDR-17 1,977,048.50 6,114,470.55 14.4 16.5 Boring

PV9 HDR-18 1,974,646.41 6,114,512.52 24.5 26.5 Boring (RW)

PV13 HDR-25

1,977,110.75 6,114,621.65

15.0

PV21 HDR-19 1,975,727.69 6,114,885.34 19.2 11.5 Boring

HDR-20 1,975,482.00 6,114,816.75 19.6 11.5 Boring

HDR-21 1,975,299.69 6,114,769.37 20.8 11.5 Boring

HDR-22 1,976,856.81 6,114,686.05 15.0 11.5 Boring

HDR-23 1,976,609.18 6,114,612.59 15.6 11.5 Boring

HDR-24 1,976,256.06 6,114,679.40 17.4 11.5 Boring

PV23 HDR-26 1,975,194.80 6,114,565.92 23.1 16.5 Boring

HDR-27 1,973,473.97 6,114,701.42 30.4 16.5 Boring

HDR-28 1,974,731.73 6,114,307.35 23.2 16.5 Boring

HDR-29 1,973,916.96 6,114,520.69 28.5 16.5 Boring

HDR-30 1,973,684.74 6,114,863.05 30.5 16.5 Boring

Drilling Methods

Pitcher Drilling Company advanced the borings using a truck-mounted Failing 1500 and CME 55 and track-mounted CME850 drill rigs using rotary wash and hollow stem auger (HSA) drilling methods. The drill rig used is stated on the boring log. Borings advanced using rotary wash methods are indicated in Table 2-1.

The rotary wash method pumps drilling fluid consisting of water and bentonite powder through the drill string and bit as drilling progresses. The drilling fluid carries cuttings to the surface and into a settling tank. The cuttings settle in the tank and the fluid is re-

March 17, 2017 | 7 circulated down the hole. The drilling fluid provides pressure to support the open walls of the borehole below the casing.

The HSA method consists of a section of seamless tube wrapped with spiral flights, an adapter cap, a center plug, and a cutting head on the lead auger. The center plug is used during drilling to reduce the chance of soil cuttings entering the center of the augers and influencing the blow count. When sampling, the driller raises the center plug from the interior of the auger stem and lowers the sampler down to the sampling point. The auger stem is left in place to act as casing to minimize caving.

CPTs

Gregg In-Situ advanced the CPTs using a truck-mounted rig with a 20-ton push capacity.

CPTs were advanced by hydraulically pushing an instrumented steel cone into the ground in general accordance with ASTM D5778. The instrumented cone assembly includes a cone tip with a 60-degree apex and a cone base area of 15 square centimeters (cm2), a friction sleeve segment with a surface area of 225 cm2, and a pore pressure transducer mounted near the base (shoulder) of the cone tip, and geophone sensors located just above the friction sleeve. Prior to the start of the test, the operator hydraulically raises the rig onto rigid feet to unload the vehicle suspension and provide a stable reaction for cone thrust. The instrumented cone is advanced through the soil at a steady rate of about 2 centimeters per second. As the cone is advanced, transducers inside the cone monitored cone tip resistance, sleeve (side) friction, and pore water pressure. This data was digitally recorded and stored during the test.

Sampling

The subsurface soils sampled in the borings at every 2 ½ foot interval until 10 feet and at 5 foot intervals after. The sampling interval was adjusted as necessary in the field based on the material encountered during the drilling. Soil samplers included 2.5-inch inside diameter Modified California (Mod Cal) split barrel sampler with liners and a 1.375-inch inside diameter Standard Penetration Test (SPT) split barrel sampler without liners to obtain samples of the subsurface material. The Mod Cal and SPT samplers were used in general accordance with ASTM D1586. The type of sampler used at each sampling interval based on the material encountered or expected to be encountered.

Mod Cal and SPT samplers were driven into the subsurface material using an automatic trip 140-pound hammer with a 30-inch free fall in general accordance with ASTM D1586.

After the sampler was driven, it was removed from the borehole and the exploration was advanced to the next sample interval. We capped Mod Cal samples to retain moisture and placed SPT samples in “Ziploc” bags. We labeled each sample with the project number, date, sample number, and depth. If more than one sample was taken at each interval, an A/B designation was added with A being the lower sample and B the upper.

Disturbed bulk samples were collected in select hollow stem auger borings for testing.

The PV4 bulk samples were composited and remolded to perform California Bearing Ratio testing required for aircraft rigid pavement design. Other hollow stem auger borings were remolded in the laboratory to perform R-value testing used in vehicular pavement design.

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A HDR field engineer maintained a boring log and visually classified the soils encountered in the samples and cuttings in accordance with ASTM D2488. The field classifications were updated based on laboratory test results in accordance with ASTM D2487. Soil undrained shear strength was measured in the field for fine grained soils using either pocket penetration and Torvane devices at the base of Mod Cal samples.

Upon completion of drilling the samples were transported to the HDR Oakland, CA office for further review.

Hammer

Resistance blow counts were obtained for the Mod Cal and SPT samplers by dropping a 140-pound, automatic hammer through a 30-inch free fall. The samplers were driven 18 inches, or a shorter distance where hard resistance was encountered, and the number of blows were recorded for each 6 inches of penetration. The vertically-stacked blows recorded on the boring logs represent the individual blows for each 6 inches of driving.

The blows per foot is the accumulated number of blows that were required to drive the last 12 inches, or the number of inches indicated where hard resistance was encountered. The field blow counts (Nf) are shown for each sample on the boring logs.

The Nf has not been corrected for the sampler size.

Drill cuttings and Site Restoration

After each boring was completed, Pitcher Drilling placed soil cuttings and drilling fluid in 55-gallon drums. The drums were temporarily stored in the gravel parking area located northwest of Building 663. Pitcher Drilling obtained composite samples from the cuttings in the drums and ran analytical testing to classify the material for disposal. Pitcher Drilling disposed of the drums at an appropriate disposal facility.

The borings were backfilled with neat cement grout in accordance with Santa Clara Valley Water District well permit requirements, with an approximate ratio of 94 pounds of Portland cement for every 6 gallons of water. Pitcher Drilling capped the borings completed on a paved surface with asphalt concrete cold patch. The remaining borings were capped with grout. All equipment, materials, and trash were removed from the site and the area was restored to its prior condition.

2.3 Project Laboratory Testing

Selected soil samples obtained during the subsurface investigation were delivered to Cooper Testing Laboratory in Palo Alto, CA for geotechnical laboratory testing.

Laboratory testing consisted of index parameters including grain size analysis (ASTM D422), Atterberg Limits (ASTM D4318), in-situ moisture and unit weight (ASTM D2216).

Additional laboratory testing included:

Eight (8) consolidation (ASTM D2435), Twelve (12) unconsolidated undrained triaxial compression (TXUU) (ASTM D2850), Five ( 5) R-Value (Caltrans, 2000), One (1) Relative Compaction (ASTM 1557)

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Four (4) California Bearing Ratio (ASTM 1883), and

Four (4) corrosivity tests that included resistivity (ASTM G57 and Cal 643), chloride (ASTM 4327), sulfate (ASTM 4327), pH (ASTM G51), sulfide (qualitative by lead acetate paper) and Redox (ASTM G200).

The results of the laboratory tests are presented on the boring logs at the appropriate sample depths and in Appendix D.

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3 Geologic Setting

3.1.1 Regional Geology

The San Francisco Bay Area lies within the Coast Ranges geomorphic province, which is a series of discontinuous northwest trending mountain ranges, ridges, and intervening valleys characterized by complex folding and faulting. The general geologic framework of the San Francisco Bay Area is illustrated in studies by Schlocker (1970), Wagner et al.

(1991), Chin et al. (1993), Ellen and Wentworth (1995), Helley et al. (1994), and Graymer et al. (2006).

Geologic and geomorphic structures within the San Francisco Bay Area are dominated by the San Andreas Fault (SAF), a right-lateral strike-slip fault that extends from the Gulf of California in Mexico to Cape Mendocino on the Coast of Humboldt County in northern California. The SAF forms the boundary between two independent tectonic plates on the surface of the earth. The Pacific and North American plates are located to the west and east of the SAF, respectively. In the San Francisco Bay Area, movement across this plate boundary is concentrated on the SAF; however, it is also distributed across a number of other faults including the Hayward, Calaveras, and Concord among others.

Together, these faults are referred to as the SAF system.

Movement along the SAF system has been ongoing for about the last 25 million years.

The northwest trend of the faults within the SAF system is largely responsible for the strong northwest structural orientation of geologic and geomorphic features in the San Francisco Bay Area. Currently, active compressional forces normal to the northwest structural trend of the Coast Range province are also partially responsible for the strong northwest structural trend and uplift of the mountains within the province. These compressional forces are responsible for the movements associated with the Great Valley fault system, a series of blind (no surface expressions of the faults are evident) thrust faults along the eastern margin of the Coast Range province and folding of the younger rocks within the region.

Basement rocks west of the SAF are generally granitic, while the basement rocks east of the SAF generally consist of a chaotic mixture of highly deformed marine sedimentary, submarine volcanic and metamorphic rocks of the Franciscan Complex. Both are typically Jurassic to Cretaceous in age (200-65.5 million years old [USGS, 2010]).

Overlying the basement rocks are Cretaceous (about 145.5 to 65.5 million years old) marine, as well as Tertiary (about 65 to 2.6 million years old) marine and non-marine sedimentary rocks with some continental volcanic rock. These Cretaceous and Tertiary rocks have typically been extensively folded and faulted as a result of Late Tertiary and Quaternary regional compressional forces. The inland valleys as well as the structural depression within which the San Francisco Bay is located are filled with unconsolidated to semi-consolidated deposits of Quaternary age (about the last 2.6 million years).

Continental surficial deposits (alluvium, colluvium, and landslide deposits) generally consist of unconsolidated to semi-consolidated sand, silt, clay, and gravel while the Bay deposits typically consist of very soft organic-rich silt and clay (Bay Mud) and sand.

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3.1.2 Site Geology

The site is located approximately 2.5 miles south of San Francisco Bay. The geology of the site and surrounding areas has been illustrated in studies conducted by Dibblee and Minch (2007) and Helley and Graymer (1997). These studies are in general agreement that the site is underlain by Holocene age (about 11,700 years or younger [USGS, 2010]) alluvial deposits.

Per Helley and Graymer (1997), the site is underlain by Holocene-age Basin Deposits (Qhb), which generally consists of very fine silty clay to clay deposits occupying flat-floored basins at the distal edge of alluvial fans adjacent to the bay mud (Qhbm). Per Dibblee and Minch (2007), the site is underlain by Holocene-age silty clay and organic clay. The geologic map of the site is shown in Figure 3-1 – Site Geology.

3.1.3 Regional Seismicity

The site is situated within a region traditionally characterized by numerous active faults and high seismic activity. Many faults exist in the region are capable of producing earthquakes, which may cause strong ground shaking at the project site. The nearest active faults to the site are listed in Table 3-1.

Table 3-1. Nearest Active Faults

Fault Distance to Site

(km) MMax Fault Type

Silver Creek 5.2 6.9 Reverse

Monte Vista-Shannon 6.7 6.7 Reverse

San Andreas 9.1 7.9 Strike-Slip

Hayward 10.1 7.3 Strike-Slip

Calaveras 13.0 6.9 Strike-Slip

An active fault is a fault that has experienced seismic activity during historic time (since roughly 1800) or exhibits evidence of surface displacement during Holocene time (Bryant and Hart, 2007). The definition of “potentially active” varies, but is generally a fault showing evidence of displacement that is older than 11,700 years (Holocene age) and younger than 2.6 million years (Pleistocene age). However, “potentially active” is no longer used as criteria for zoning by the California Geologic Society (CGS). The terms “sufficiently active” and “well-defined” are now used by the CGS as criteria for zoning faults under the Alquist-Priolo Earthquake Fault Act. A “sufficiently active fault” is a fault that shows evidence of Holocene surface displacement along one or more of its segments and branches, while a “well-defined fault” is a fault whose trace is clearly detectable by a trained geologist as a physical feature at or just below the ground surface.

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3.2 Geologic Hazards

3.2.1 Fault Rupture

Based on the information provided in Bryant and Hart (2007) and CGS (2000) and the Caltrans ARS on-line report (V2.3.06), the site is not located within a currently designated Alquist-Priolo Earthquake Fault Zone and no active faults are known to traverse the site. The nearest fault zone is the Cascade Fault located 4.2 miles southwest from the site and the nearest active fault zone is the Silver Creek Fault located

5.2 miles southwest from the site as shown on Figure 3-2 – Regional Fault Map. The potential for fault-related ground surface rupture at the site is low.

3.2.2 Liquefaction

Earthquake-induced soil liquefaction can be described as a significant loss of soil strength and stiffness caused by an increase in pore water pressure resulting from cyclic loading during shaking. Liquefaction is associated primarily with loose (low density), saturated, fine- to medium-grained, cohesionless soils below the groundwater table, but can also occur in non-plastic to low-plasticity finer grained soils. The potential consequences of liquefaction to engineered structures include loss of bearing capacity, buoyancy forces on underground structures, ground oscillations or “cyclic mobility”, increased lateral earth pressures on retaining walls, liquefaction settlement, and lateral spreading or “flow failures” in slopes.

The site is located within a State of California Seismic Hazard Zones for liquefaction as shown on Figure 3-3 – Seismic Hazards Zone Map. These areas are where historical occurrences of liquefaction, or local geological, geotechnical and ground-water conditions indicate a potential for permanent ground displacements such that mitigation as defined in Public Resources Code Section 2693(c) would be required (CGS, 2003).

The potential for liquefaction at the site is moderate. The liquefaction analysis is discussed in Section 5.

3.2.3 Seiches and Tsunamis

Seiches are large waves generated in enclosed bodies of water in response to ground shaking and tsunamis are waves generated in large bodies of water by fault displacement or major ground movement. The tsunami inundation maps for emergency planning (CalEMA, 2009) is shown on Figure 3-4 – Tsunami Inundation Map. This map indicates that tsunami-generated waves will not reach the site area due to its distance from the San Francisco Bay and unprotected water courses. Based on this map and the absence of enclosed bodies of water near the site, seiche and tsunami risks at the site are considered negligible.

3.3 Flooding

The Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps for the site (FEMA, 2010) indicate the project site is mapped as Zone D, which is an area where the flood hazard has not been determined as shown on Figure 3-5 – FEMA Flood Map. However, Moffett Field is mapped as surrounded by areas of 2 percent chance of

March 17, 2017 | 13 annual flooding. The 2 percent annual chance flood is the flood that has a 2 percent chance of being equaled or exceeded in any given year (200-year flood). The governing agency should be consulted to establish the base flood elevation to be used for design.

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4 Site Conditions

4.1 Surface Conditions

The site is located east of Macon Road and west of the Moffett Field taxi way in the southeast area of Moffett Field. The site is irregular in shape and about 5,000 feet at its longest dimension and about 1,000 feet at its widest dimension. The site extends up to but does not include the eastern most airfield taxi way, Hangers 2 and 3 to the north and the security fence line on the east and south.

Site elevations range from about Elevation 33 feet at the southern end and about Elevation 14 feet at the northern end. The site has 17 structures ranging in size from 336 to 62,572 square feet, associated parking, landscaped areas, and open fields shown on Exhibits 2-1 through 2-3. The existing structures were constructed between 1943 and 2014. Exhibit 4-1 is a photograph taken north of the Pararescue Operations Building 663 (adjacent to PV3 and PV6) showing the typical general site conditions of existing structures, parking lot and an open field area.

Exhibit 4-1. General Site Conditions

4.2 Subsurface Conditions

As previously discussed, the site is mapped as being underlain by Holocene-age Basin Deposits located at the distal edge of alluvial fan deposits consisting of fine grained soils.

Subsurface conditions encountered during this investigation and as documented in historical explorations found that the site is underlain by alluvial fan deposits consisting of fine grained soils interlayered with variable thickness discontinuous sand layers. The

March 17, 2017 | 15 sand layers are most prevalent in the upper 20 feet. In general the site can be broadly divided into three stratigraphic zones.

An upper zone (upper 8 to 12 feet) consisting of fill overlying high plasticity Fat Clay and lower plasticity Lean Clay with some discontinuous sand layers.

A middle zone (at a depth of 10 to 25 feet) consisting of interlayers Lean Clay, Sand, Silty Sand, Clayey Sand and sandy Gravel.

A lower zone (below 20-foot depth) consisting of predominately Lean Clay.

Figures 4-1 through 4-5 present cross sections at the proposed building locations and are discussed below.

Figure 4-1 - Cross-Section A-A’: Subsurface conditions for PV4/7 and PV2 located in the northern area of the site. Near surface subsurface conditions consists of 0 to 7 feet of medium stiff to stiff fill consisting of lean clay with varying amount of sand and gravel.

The fill overlies 2 to 5 feet of medium stiff fat clay overlying soft to stiff lean clay with varying amounts of sand with interbedded layers of sand to a depth of 25 feet. Below a depth of 25 the subsurface conditions are predominately lean clay.

Figure 4-2 –Cross-Section B-B’: This cross section is focused on shallow hollow stem auger borings performed for the PV4 Hangar floor. In borings HDR-31 through HDR-36, a coarse-grained layer starting at about 4 to 9 feet and ending at about 8 to the maximum depth explored at 16 ½ feet. This layer could extend to a depth of 25 feet as shown in Cross Section A-A’. As typical for alluvial fan deposits the coarse-grained layer has a variable thickness and consistency, ranging from low fines content sand to a clayed sand. The layer is laterally discontinuous likely representing a series of depositional meanders. The layer was not encountered in boring HDR-37. The coarse-grained layer was encountered in HDR-8 from about 5 to 7 feet and 11 to 13 feet, HDR- 10 from about 7 to 8 feet, and HDR-16 from about 7 to 12 feet. Heaving of the sand and gravel layers were noted in the hollow stem augers. Exploration HDR-8, HDR-10, and HDR-16 are the deeper explorations performed for PV4 and PV7 (located adjacent to

PV4).

Figure 4-3 – Cross-Section C-C’ And Figure 4-4 – Cross-Section D-D’: Subsurface conditions for the PV3/6 which is located in the central area of the site. Cross-Section C- C’ was drawn in the North-South direction and includes the PV9 subsurface conditions.

Cross-Section D-D’ was drawn in the West-East direction. Near surface conditions consist of 3 to 9 feet of fat clay underlain by lean clay to a depth of 12 feet. There is a central area where a portion of the fat clay was removed and replaced with fill consisting of stiff to very stiff sandy lean. A coarse grained layer, consisting of sand and silty sand was encountered in the vicinity of PV 6, in borings HDR-5, HDR-14 and CPT HDR-6 in Figures 4-3. The coarse grained layer was found to extend laterally in an east west direction (Figure 4-4) and was encountered in borings HDR-13 and HDR-26. Below a depth of 20 feet the site is underlain by lean clay to the depths explored.

Figure 4-5 – Cross-Section E-E: Subsurface conditions for the PV5 area which is located in the southern area of the site. The southern area is underlain by about 4 to 5 feet of very stiff fat clay over medium stiff to very stiff lean clay that extended to the depths explored. Explorations HDR-11, HDR-12 and HDR-27 encountered a sand layer at

16 | March 17, 2017 depths of 4 to 9 feet. Sand layers were also encountered in HDR-11 at depths of 26 to 28 feet and 41 to 43 feet.

4.3 Groundwater

A summary of the depth to groundwater measured during the field investigation performed for this Project is presented in Table 4-1. Measurements were taken at the time of drilling and may not have reach equilibrium conditions. Measurements are reported to the nearest ½-foot depth from the top of borehole.

Table 4-1. Groundwater Elevations

Exploration

Approximate Surface Elevation

(feet)

Approximate Depth to Groundwater 1

(feet)

Approximate Groundwater Elevation

(feet)

HDR-01 18 10 8

HDR-02 19 10 9

HDR-04 21 7.5 13.5

HDR-12 31 7 24

HDR-13 21 7.5 13.5

HDR-14 21 8 13

HDR-17 15 11 4

HDR-19 19 6.5 12.5

HDR-21 20 6 14

HDR-22 15 10 5

HDR-23 16 7.5 8.5

HDR-25 16 10 6

HDR-26 21 7.5 13.5

HDR-28 23 10 13

HDR-29 28 13 15

HDR-30 29 9.5 19.5

HDR-31 17 5.5 11.5

HDR-32 16 6 10

HDR-33 16 5 11

HDR-34 15 6 9

HDR-39 32 13 19

1. Groundwater measured at the time of drilling

We encountered the groundwater at depths ranging from about 5 to 13 feet (Elevation of 4 to 24 feet) at the time of the investigation. Groundwater elevation generally followed the site topography and was encountered at shallower elevations in the northern (Elevation 4 to 12 feet) and deeper elevations in the south (Elevation 19 to 24 feet).

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5 Discussions and Conclusions

5.1 General

5.1.1 Liquefaction

Liquefaction evaluations were based on both CPT and rotary wash borings performed for this investigation. For the soil layers encountered in our mud rotatory borings, the soil composition criteria in Seed et al. (2003) was used to evaluate the liquefaction susceptibility. For soil layers determined to be potentially liquefiable, we performed a liquefaction triggering analyses using the methodologies in Idriss and Boulanger (2008).

We estimated the liquefaction induced settlements using criteria in Tokimatsu and Seed (1987). For the CPTs, the computer program CLiq (Version 1.7.5.27) was used to perform the liquefaction triggering analyses and liquefaction induced settlement calculation. Liquefaction analysis using CPT data relies on correlations to determine the soils consistency including the normalized Soil Behavior Type (Ic). The subsurface conditions at the site have many thin, discontinuous, high fines content clayey sands that are in the transition between fine grained and coarse grained soils, and would likely be misinterpreted as liquefiable by standard CPT data reduction techniques. Therefore, the liquefaction analysis was performed only for those soils that have an Ic value of less than

2.3 to screen these layers. The depth to groundwater measured at the time of drilling was used in the analysis. If the exploration method did not allow for groundwater measurement, we used the depth to groundwater from adjacent explorations.

Earthquake magnitude (Mw) and peak ground acceleration (PGA) were determined using the 2008 Probabilistic Seismic Hazard Analysis (PSHA) Interactive Deaggregation website (https://geohazards.usgs.gov/deaggint/2008/). The analysis used a Mw = 6.79 and a PGA = 0.472g for the liquefaction analysis. We did not perform a site-specific ground motion hazard analysis, but the Mw and PGA estimated from the PSHA website matched the values from the site-specific ground motion hazard analysis presented in Kleinfelder (2015) for a project located on the northwest side of Moffett Field.

The minimum factors of safety for liquefaction potential is defined in UFC 3-220-01 Section 2-1.1.1 Table 2.1 by risk category with the minimum factor of safety of 1.0 for risk category I and II and 1.1 for risk categories III and IV as defined in Uniform Building Code Table 1604.5. It is assumed that all strucutres will be designated either III or IV.

The site is comprised predominately of medium stiff to very stiff lean clay of moderate plasticity and therefore non-liquefiable based on soil composition criteria presented in Seed et al. (2003). Zones of loose to medium dense sand between depths of about 10 to 20 feet bgs were encountered beneath PV 4 and PV3/PV6. The liquefaction triggering analyses showed this sand layer is liquefiable, an if not mitigated, could induce additional footing settlement greater than allowed per UFC 3-222-01 Section 1808.2 which limits total settlement to not more than 1 inch and angular distortion will be limited to 1/500 unless otherwise authorized by the building official. Calculated post-liquefaction settlements range from less than 0 inch to 3 inches. A discussion of the liquefaction analyses for each PV# is discussed in the following section and the calculation sheets are included in Appendix E.

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5.1.2 Foundation Support

Shallow Foundations

Shallow foundations should have an adequate safety factor against bearing failure and limit vertical movements of the foundation due to total settlement (immediate elastic, consolidation and seismically-induced) of the foundation soils. Per UFC 3-220-01 Section 2-3.8.1, total settlements should not exceed 1 inch and angular distortion should not exceed 1/500. Also per UFC 3-220-01, the minimum width for continuous footings shall be 18 inches wide or 8 inches wider than the supported wall, whichever is greater, and the minimum depth shall be 18 inches below lowest adjacent grade. If the calculated settlement was greater than 1 inch, the structure should be founded on deep foundations or the ground improved to provide foundation support.

Minimum factors of safety to determine allowable bearing capacity for shallow foundations bearing on soil are provided in UFC 3-220-01 Section 2-3.6.1 Table 2.2 that indicates a minimum factor of safety of 3 should be used for design.

Allowable Bearing Pressure

We evaluated the bearing capacity for each structure using Terzaghi’s bearing capacity formulas and factors. The formulas use cohesion, effective unit weight of the soil, and the dimensions of the footing. The factors are based on the effective friction angle (’) of the soil. We determined the ’ using published relationships between Plasticity Index (PI) for cohesive soils and the equivalent blow count (N1)60 for cohesionless soils.

We used the relationship presented in Bjerrum and Simons (1960) to determine the ’ for cohesive soils shown on Exhibit 5-1.

Exhibit 5-1. ’ of Cohesive Soils Based on PI

March 17, 2017 | 19

We used the relationship presented in Hatanaka and Uchida (1996) to determine the ’ for cohesionless soils shown on Exhibit 5-2.

Exhibit 5-2. Effective Friction Angle of Sand Based on SPT Resistance

Nf blow counts presented on the boring logs (Appendix C) were corrected to (N1)60 using the equation presented in Idriss and Boulanger (2008):

Settlement

Settlement for each PV# was calculated based on a soil profile developed from the explorations performed at or near the PV#, results of laboratory consolidations and current understanding of loads provided by the structural engineers. Results of consolidation testing indicate that the soils have been consolidated with maximum past pressures from 3,000 to 4,500 psf. These maximum past pressure values are similar to the values presented in AGS (2011) prepared for Building 663. Consolidation test result from HDR-9 sample from 60 feet bgs was not included in these analyses because this sample appeared to be disturbed.

Lateral Load Resistance

UFC 3-220-1 Section 2-3.7.3 requires that The factor of safety against sliding, calculated as the ratio of forces resisting movement to the horizontal component of earth plus water pressure on the back wall, whether in soil or rock shall be not less than 2.0. In rock, the sliding seismic loading factor of safety is 1.3.

Deep Foundations

Minimum factors of safety for deep foundations are provided in UFC 3-220-01 Section 2-

3.6.1 Table 2.2 that indicates a minimum factor of safety of 3 should be used for design if load testing is not to be performed. The lateral and axial capacities of the deep foundations were evaluated assuming 18-inch diameter Auger Cast Piles (ACP) would

20 | March 17, 2017 be the preferred alternative. Axial capacities for 12-inch and 14-inch prestressed concrete piles were also evaluated. Other pile types are feasible from a geotechnical engineering standpoint, such as pipe pile, steel H-pile and specialty piles such as auger cast displacement piles (ACDP) or screw in displacement piles and can be evaluated if requested. Cranes and other tall equipment used to install deep foundations should comply with the requirements of UFC 3- 260-01 including equipment height, clearance and marking requirements.

Lateral Pile Capacity

We used the computer program LPILE Plus Version 6.0 (Ensoft, 2016a) for single piles for pile groups to develop the lateral capacity. We input soil properties to generate soil resistance curves (p-y curves) as a function of pile deflection. The resistance-displacement characteristics of near-surface soils and the material strength of piles govern the lateral resistance and deflections of vertical pile foundations. We performed the lateral pile analyses using an un-cracked pile section and design concrete strength (f’c) of 4000 pounds per square inch (psi) with fixed head conditions. We applied top deflections of ¼, ½, and 1-inch corresponding to the lateral deflection needed to mobilize passive resistance against the sides of the pile caps.

Axial Pile Capacity

Allowable pile capacity was evaluated for 14-inch diameter auger cast piles (ACP) using methods presented in the Federal Highway Administration – Drilled Shafts (FHWA, 2010). The contribution from end bearing was ignored. Shaft frictional resistance in fine grained soils was base on undrained shear strength estimated from the CPTs and triaxial laboratory test results. A factor of Safety of 3 was applied oin accordance with UFC criteria of non-load tested piles.

Allowable pile capacity of both 12-inch and 14-inch square prestressed concrete driven piles was also calculated using the computer program CPTeT-IT (version 2.0.1.52) based upon interpretation of the CPT data Allowable capacity was calculated using a factor of safety of 3 for both shaft resistance and end bearing in accordance with UFC criteria for non load tested piles. For allowable tension capacity under transient flood, wind or seismic conditions a safety factor of 1.5 may be used. For allowable sustained tension a safety factor of 3 may be used.

Pile Settlement

We expect post-construction settlement to be less than ½ inch for piles installed according to recommended procedures. This settlement estimate is from the settlement of the soils and elastic compression of piles.

Effect of Liquefaction

Based on the findings from our geotechnical exploration program, the site is comprised predominately of non-liquefiable lean clays. Potentially liquefiable sand layer were encountered at depths of 10 to 20 feet in a majority of the explorations.