Geo_Report_091117.pdf

GEOTECHNIAL INVESTIGATION REPORT

VEHICLE MAINTENANCE FACILITY

CALIFORNIA AIR NATIONAL GUARD

MOFFETT FEDERAL AIRFIELD

MOUNTAIN VIEW, CALIFORNIA

(DRAFT)

For

MEAD & HUNT, INC.

9600 NE Cascade Parkway, Suite 100 Portland, OR 97220

September 2014 Job No. 2014-123-010

PARIKH CONSULTANTS, INC.

2360 Qume Drive, Suite A, San Jose, CA 95131

(408) 452-9000

TABLE OF CONTENTS

Page No.

1.0 INTRODUCTION

2.0 PURPOSE AND SCOPE

3.0 EXISTING FACILITIY AND PROPOSED CONSTRUCTION

4.0 SITE CONDITIONS

5.0 FIELD EXPLORATION AND LABORATORY TESTING

6.0 SUBSURFACE SOIL CONDITIONS

7.0 GEOLOGY

8.0 EARTHQUAKE CONSIDERATIONS

8.1 Seismic Sources

8.2 Seismic Design Criteria for Buildings

8.3 Seismic Hazards/Liquefaction Potential

9.0 FINDINGS AND RECOMMENDATIONS

9.1 General

9.2 Earthwork and Grading

9.3 Foundation Design for Buildings

9.4 Slabs-on-grade

9.5 Drainage

9.6 Subgrade Improvement

9.7 Utility Trench

9.8 Structural Pavement Design

9.9 Corrosion

10.0 PLAN REVIEW

11.0 CONSTRUCTION OBSERVATION

12.0 INVESTIGATION LIMITATIONS

PLATES

Project Location Map ................................................................................................................... Plate 1

Site Plan ....................................................................................................................................... Plate 2

TABLE OF CONTENTS (CONTINUED)

Geologic Map ............................................................................................................................... Plate 3

Fault Map ..................................................................................................................................... Plate 4

APPENDICES

APPENDIX A

Log of Borings

APPENDIX B

Laboratory Test ........................................................................................................................ Plate B-1

Plasticity Chart ................................................................................................................... Plate B-2 Grain Size Distribution Curves .................................................................... Plates B-3A and B-3B Unconfined Compressive Strength Tests .............................................. Plates B-4A through B-4G R-Value Tests ............................................................................................... Plates B-5A and B-5B Corrosion Tests ............................................................................................. Plates B-6A and B-6B

APPENDIX C

Evaluation of Liquefaction Potential

GEOTECHNCIAL INVESTIGATION REPORT

VEHICLE MAINTENANCE FACILITY CALIFORNIA AIR NATIONAL GUARD

MOFFETT FEDERAL AIRFIELD

MOUNTAIN VIEW, CALIFORNIA

1.0 INTRODUCTION

This report presents the results of our geotechnical engineering investigation performed for the proposed “Vehicle Maintenance Facility California Air National Guard Moffett Federal Airfield” project in Mountain View, California, hereinafter referred to as “PROJECT”. The work was performed in general accordance with the scope of work outlined in our proposal to Mead & Hunt, Inc. (Designer). The approximate location of the project site and its vicinity are shown on the Project Location Map, Plate 1.

The geotechnical recommendations presented in this report are intended for design input and are not intended to be used as specifications. In addition, the data provided in this report including these geotechnical recommendations should not be used for bidding purposes or for construction cost estimates. If the report is provided as a reference document, any interpretation of the data and recommendations should be the sole responsibility of the user and PARIKH Consultants, Inc. (PARIKH) shall not be liable for any consequences.

2.0 PURPOSE AND SCOPE

The purpose of this investigation was to evaluate the general subsurface soil conditions at the project site, to evaluate their engineering properties, and to provide geotechnical recommendations for the foundation design of the vehicle maintenance building and vehicle storage building of the proposed project.

The scope of work performed for this investigation included site reconnaissance; obtaining representative soil samples and logging soil materials encountered in the soil borings;

laboratory testing of the collected soil samples, performing engineering analyses based on the field and laboratory data, and preparation of this geotechnical investigation report.

3.0 EXISTING FACILITY AND PROPOSED CONSTRUCTION

Existing Facility

The existing project site is the Greenfield site. There is no existing facility at the site.

Mead & Hunt, Inc. **DRAFT**

Vehicle Maintenance Facility California Air National Guard Moffett Federal Airfield Project No. 2014-123-010 September 2014

Proposed Construction

The project will include:

Parking for privately owned vehicle.

Pedestrian walkway from the parking area to the administration building.

Vehicle storage area, both covered and uncovered, for maintenance vehicle.

Drive lanes and aprons for vehicular movements; and

Site lighting and landscaping.

Our recommendations presented in this report are based on the above information. Any major deviation should be reported to PARIKH for further consideration.

4.0 EXISTING SITE CONDITIONS

The site is located on the east side of Moffett Federal Airfield west of and adjacent to Macon Road. The existing site is currently an undeveloped grass field. The site generally drains from south to north and the topography is fairly flat.

The following are the existing utilities within the project site:

1. Water main crosses the Vehicle Maintenance site from east-west along the south edge of the site.

2. Sanitary gravity main runs north-south along the western side of Macon Road

3. New sanitary service to the Pararescue facility runs east-west along the north side of the site.

4. Gas main runs along the west side of the site.

5.0 FIELD EXPLORATION AND LABORATORY TESTING

The field exploration program was developed based on discussions with the designer. A total

Project No. 2014-123-010 of four borings (Borings B-1 through B-4) were drilled to the depths between 30 feet and 44.5 feet in August 2014.

The approximate locations of the borings are shown in the “Boring Location Plan”, Plate 2.

The details of the field exploration are included in Appendix A. The descriptions of the materials encountered in the field exploration are shown on the "Log of Borings".

Laboratory tests were performed on selected soil samples collected during field exploration to evaluate the physical and engineering properties of the subsurface soils. The laboratory test methods and test results are presented on plates included in Appendix B. Laboratory test results for moisture content, total unit weight, unconfined compression, Plasticity Index and grain size classification of the soil samples are presented on the Log of Borings in Appendix A.

It should be noted that the descriptions of the soils encountered and relevant boring information presented on the Log of Borings depict subsurface conditions only at the locations indicated on the plan and on the particular date noted on the Log of Borings. Because of the variability from place to place within soil/rock in general, subsurface conditions at other locations may differ from conditions occurring at the boring locations explored. The abrupt stratum changes shown on the logs may be gradational and relatively minor changes in soil types within a stratum may not be noted on the logs due to field limitations. Also, the passage of time may result in a change in the soil conditions at these locations due to environmental changes.

Due to limitations inherent in geotechnical investigations, it is neither uncommon to encounter unforeseen variations in the subsurface soil conditions during construction nor is it practical to determine all such variations during an acceptable program of drilling and sampling for a project of this scope. Such variations, when encountered, generally require additional engineering services to attain properly constructed project. We, therefore, recommend that a contingency fund be provided to accommodate any additional charges resulting from technical services that may be required during construction.

Project No. 2014-123-010

6.0 SUBSURFACE SOIL CONDITIONS

Based on the boring data of Borings B-1 through B-4, the subsurface soil conditions encountered in the soil borings within the project site are summarized in the table below.

TABLE 1: SUMMARY OF SUBSURFACE SOIL CONDITIONS

Boring

No.

Boring

Depth (ft)

Subsurface Soil Conditions

B-1 30 Approximately 12 feet of medium stiff to very stiff lean clay, underlain by approximately 5 feet of medium dense sand, underlain by medium stiff to very stiff lean clay to the boring depth.

B-2 44.5 Approximately 12 feet of medium stiff to stiff lean clay, underlain by a thin layer of loose sand, underlain by medium stiff to very stiff lean clay to the boring depth.

B-3 30 Approximately 15 feet of medium stiff to very stiff lean clay, underlain by approximately 3 feet of medium dense sand, underlain by medium stiff to stiff lean clay to the boring depth.

B-4 30 Approximately 8 feet of stiff lean clay, underlain by approximately 11 feet of medium dense sand, underlain by medium stiff to stiff lean clay to the boring depth.

Groundwater was measured at approximate depths of 7 to 8 feet in these borings.

Based on the “Seismic Hazard Zone Report – Mountain View 7.5’ Quadrangle Plate 1.2 – Groundwater”, the depth to historically high groundwater is estimated to be approximately 0 feet. Design groundwater elevation of +19 feet (approximately 3 feet from highest ground elevation of soil boring which is +22 feet of Boring B-1) is assumed for this project.

Groundwater level is anticipated to vary with the passage of time due to seasonal and climatic variation, fluctuation of water elevations in the nearby creek(s), surface and subsurface flows, ground surface run-off, and other environmental factors, which may not be present at the time of the investigation. Groundwater levels also tend to fluctuate with construction activities. As such, the groundwater table should be checked immediately prior to construction to assess its effect on site work and other construction activities.

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7.0 GEOLOGY

The project site is in the southwestern portion of San Francisco Bay area in the Coast Range geomorphic province of California. The Coast Range forms a nearly continuous topographic barrier between the California coastline and the San Joaquin Valley. The Coast Range in this region is a double chain of mountain running north-northwest. Three prominent geologic blocks dominate the San Francisco Bay Area: the Santa Cruz Mountains (western block), the San Francisco Bay (central block), and the East Bay Hills/Diablo range (eastern block).

General geologic features pertaining to the project site and its vicinity were evaluated with reference to the Geologic Map titled “Geology Map of the Palo Alto and Mountain View quadrangle, Alameda, San Mateo, Santa Clara Counties, California - 2007”, Dibblee, T.W., and Minch, J.A.: Dibblee Geological Foundation Dibblee Foundation Map DF-350, scale 1:24,000. Based on the map, the project site is primarily underlain by Alluvial Fans and Fluvial Deposits (Qac and Qya). The general geology of the project area is shown on the Geologic Map, Plate 3. Descriptions of the main geologic units are as follows:

Qac - Alluvial Fans and Fluvial Deposits (Holocene): Silty clay and organic clay.

Qya - Alluvial Fans and Fluvial Deposits (Holocene): Alluvial sand, fine-grained, silt and clay.

8.0 EARTHQUAKE CONSIDERATIONS

8.1 Seismic Sources

The project is located in a seismically active part of Northern California. Many faults exist in the regional area. These faults are capable of producing earthquakes and may cause strong ground shaking at the project site. Faults in the vicinity of the site with a moderate to high potential for releasing seismic energy include the Cascade Fault, San Andreas Fault Zone, Monte Vista-Shannon, Silver Creek fault and Hayward fault. The attached Fault Map (Plate 4) presents the locations of the fault systems relative to the project site.

Project No. 2014-123-010

Maximum moment magnitudes (Mmax) of some of the closest faults in the area are based on the Caltrans ARS Online Report (V2.3.06). These maximum moment magnitudes represent the largest earthquake a fault is capable of generating and is related to the seismic moment. The earthquake data of the active faults in the project vicinity are summarized in the table below.

TABLE 2: EARTHQUAKE DATA

Fault (Fault ID) Site-to-Fault

Distance, Rrup* (km)

Fault

Type

Maximum Moment

Magnitude of Fault, MMax

Cascade fault (153) 6.2 Rev 6.7 Silver Creek (148) 7.4 Rev 6.9 Monte Vista-Shannon Fault Zone (154)

6.4 Rev 6.4

Hayward (South) (137) 14.7 SS 7.3 San Andreas (Peninsula) 2011

CFM (134)

15.7 SS 8.0

*Closest distance (km) to the fault rupture plane

The Caltrans Fault Map (Plate 4) presents the locations of the fault systems relative to the project site.

8.2 Seismic Design Criteria for Buildings

It is our understanding that seismic design of the project will follow the International Building Code (IBC) without California modifications. Based on the subsurface data, it is our opinion that the subsoil can be categorized as Soil Type D (“Stiff Soil”) per NEHRP criteria. The Soil Type D is determined based on boring drilled within the project area. The shear wave velocity for individual layers were estimated based on the formulations given in Caltrans Geotechnical Services Documents and Tools:

Methodology for Developing Design Response Spectrum for Use in Seismic Design Recommendations (November, 2009) on Seismic Parameters. The average shear wave velocity for the upper 100 ft and seismic soil type were estimated in accordance with

IBC 2012.

Based on the 2012 International Building Code (IBC) and existing boring data, the relevant seismic coefficients per 2012 IBC seismic criteria are shown as follows:

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Table 3: Seismic Design Criteria per IBC (2012 International Building Code)

Coefficient Recommended Value (g)

Site Coefficient, Fa 1.00

Site Coefficient, Fv 1.50

Ss 1.50

S1 0.60

Sms=Fa*Ss 1.50

Sm1=Fv*S1 0.90

Sds=2/3*Sms 1.00

Sd1=2/3*Sm1 0.60 *Approximate Site Coordinate = 37.4085°N 122.0389°W

8.3 Seismic Hazards/Liquefaction Potential

Seismic Hazards

Potential seismic hazards may arise from three sources: surface fault rupture, ground shaking and liquefaction. Since no active faults pass through the site, the potential for fault rupture is relatively low. As shown on the Fault Map, Plate No. 4, the closest active fault is the Cascade Fault, which is located approximately 3.9 miles southwest from the project site. Based on available geological and seismic data, the possibility of the site to experience strong ground shaking may be considered moderate to high.

Liquefaction Potential

Liquefaction is a phenomenon in which saturated cohesionless soils are subject to a temporary but essentially total loss of shear strength under the reversing, cyclic shear stresses associated with earthquake shaking. Submerged cohesionless sands and silts of low relative density are the type of soils, which usually are susceptible to liquefaction. Clays are generally not susceptible to liquefaction.

Based on the available boring information, the subsurface soil conditions at the project site consist of mainly medium stiff to very stiff lean clay with intermittent pocket/lens/layer of loose to medium dense sands. Groundwater was encountered at the

Project No. 2014-123-010 depths of 7 feet and 7.5 feet in the borings during drilling.

The liquefaction potential was evaluated in accordance with the methods proposed by Youd, et al. (2001). The evaluation was primarily using the selected boring data of Borings B-1 through B-4, on the nearby Cascade Fault with a Magnitude 6.7 earthquake and a peak ground acceleration of about 0.60 g. This method compares the estimates of the earthquake-induced shear stress to the susceptibility of soil liquefaction. According to Bray (Bray, 2006), for soils with sufficient fines content so as to separate the coarser particles and control behavior, liquefaction appears to occur in soils where these fines are ether non-plastic or are low plasticity silts and/or silty clays (PI<12%, and LL<37%), and with high water content relative to their liquid limit (w>0.85 LL).

Based on the evaluation, the liquefaction potential and estimated post-liquefaction settlement at the project site are summarized in the table below.

Table 4: Summary of Evaluation of Post-Liquefaction Settlement

Boring

No.

Potentially Liquefiable Soil Estimated Post-Liquefaction Settlement (inch)

Depth (ft) Thickness (ft)

B-1 Not encountered - -

B-2 13.0 2.5 0.48

B-3 14.5 3.0 0.59

B-4 9.5 4.0 0.90

The potentially liquefiable soil appears to be in form of isolated pocket/lens and not in form of continuous layer.

The potentially liquefiable soil pocket/lens is covered by predominantly cohesive soils, which tend to serve as a “soil mat”. Spread footing or mat foundation is recommended as the foundation system so that the foundation system will not get into the potentially liquefiable soil pocket/lens.

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9.0 FINDINGS AND RECOMMENDATIONS

9.1 General

This report was prepared specifically for the proposed project. Normal construction procedures were assumed throughout our analyses and represent one of the bases of recommendations presented herein. Our design criteria have been based upon the materials and conditions encountered in the soil borings. Therefore, we should be notified in the event that these conditions are changed, so as to modify or amend our recommendations.

9.2 Earthwork and Grading

All earthwork and grading operations should be performed in accordance with the project plans and specifications. The prepared subgrade and compacted fill materials should be tested for their moisture content and density. All grading should be performed under the observation of the Geotechnical Engineer or Regulatory Agency.

Prior to the commencement of grading operations, it will be necessary to completely remove any trees, shrubs and their root systems, and strip all existing vegetation from areas to be developed. Depressions resulting from such removal and other construction activities should also be backfilled and properly compacted as discussed in the following sections.

Areas to receive engineered fill should be excavated to remove any loose/soft soil materials. The resulting surface upon which fill is to be placed should be observed by the Geotechnical Engineer or the Regulatory Agency. Areas receiving fill should be scarified to a depth of 6 inches, moisture conditioned and compacted as discussed in the following sections. This prepared subgrade should be sealed and kept moist before receiving engineered fill. All engineered fill should also conform to these preparation guidelines. Should there be any alterations of the proposed construction, which will affect the stated bases of our recommendations, we should be informed so that PARIKH can review such changes and amend or submit additional recommendations.

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Engineered Fill

In general, all engineered fill materials imported to the site should be:

Relatively non-expansive granular material with maximum Plasticity Index (P.I.)

of 15 and a Sand Equivalent (SE) value of not less than 20.

No more than 35% by dry weight passing through a No. 200 sieve.

Free of organic and inorganic debris.

Rocks or cobbles in the engineered fill should be broken down and shall not exceed 3 inches in size.

The recommended engineered fill below the slab-on-grade construction (Section

9.4 of the report) should consist of Aggregate Subbase (Class 4) conforming to Caltrans standard specifications.

The imported engineered fill should be reviewed by the Geotechnical Engineer. The native materials exposed after the excavation may be used for engineered fill provided that they meet the above criteria (P.I. and SE) and are not contaminated.

Compaction of Engineered Fill and Subgrade

The recommendations for required compaction as per ASTM D1557-91 are as follows:

90% for backfilling after removing trees, buried utilities and structures, depressions caused due to other construction activities, etc.

90% for subgrade receiving engineered fill.

90% for material below 6 inches of the footing and pavement subgrade.

95% for upper 6 inches of footing and pavement subgrade.

95% for engineered fill under slabs-on-grade.

The engineered fill should be compacted in lifts that do not exceed 8 inches in loose thickness. The compaction moisture content of the fill material should be within a

Project No. 2014-123-010 range of 2% dry of optimum moisture content to 3% wet of optimum moisture content.

PARIKH should review the final grading plans prior to grading to confirm that the intent of our recommendations is included in the plans.

9.3 Foundation Design for Buildings

As discussed in Section 8.3, shallow foundation such as spread footing or mat foundation is recommended as the foundation system for the proposed buildings considering:

a) The loading should be relatively small for the proposed buildings.

b) The potential liquefaction at the project site. Drilled pier or pile foundation system is not recommended since it may supported on the potentially liquefiable soil pocket/lens.

No foundation subgrade elevation is not yet available, it is our understanding that the proposed buildings will be supported on the native soil. The bottom of footing is recommended to be at a minimum of 2 feet below adjacent finish grade. Based on the available boring information, the subsurface soil conditions at the foundation subgrade is anticipated to consist of soft to stiff lean clay.

Spread Footing

The buildings can be supported on a conventional spread footing foundation established on native soil. The following are recommended for the spread footings:

Allowable Bearing Capacity: 900 psf (assuming a Factor of Safety of 3.0)

Passive Resistance (ultimate): 310 pcf Equivalent Fluid Pressure (EFP) (acting on the sides of the footing at a minimum displacement of 2 percent of thickness of the footing)

Friction Coefficient below footing: 0.3 (between footing bottom and medium stiff/stiff clay)

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The above allowable bearing capacities for dead plus live loads may be increased by one-third for short term seismic and wind loads.

The spread footings should be connected together to minimize any potential post-liquefaction differential settlements.

Modulus of Vertical Subgrade Reaction for Buildings

The mat foundation should have a minimum thickness of 12 inches. For these conditions, the recommended allowable bearing capacities should be as recommended for the spread footing above. The mat foundation may be designed for a modulus of vertical subgrade reaction of 19 lbs/inch3.

The mat foundation should be underlain with 6-inch of ¾-inch crushed rock.

9.4 Slabs-on-grade

The backfill against the slab should be compacted and graded to shed away from the slab perimeter using non-expansive soil. The slab should be found on minimum 18 inches compacted fill consisting of Aggregate Subbase (AS). If moisture migration through the slabs is undesirable, a moisture barrier and capillary break may be provided between the slab and the compacted layer of engineered fill. The capillary break consists of 4 inches of free draining pea gravel or clean crushed rock. A moisture barrier is generally an imperious membrane, which should be placed over the capillary break. The membrane should be covered with a 2-inch layer of sand to protect it during construction. The sand should be slightly moist just prior to pouring the slab to aid in curing the concrete.

Minor cracking and maintenance problems may be anticipated for slab-on-grade construction; however, separation from structure with concentrated loads and keeping the subgrade moist during construction can greatly reduce the amount of eventual cracking. Prior to concrete placement, any dry cracked subgrade should be sealed with appropriate watering or should be excavated and re-compacted. These conditions and construction procedures should be observed by the project Geotechnical Engineer.

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9.5 Drainage

Since soils are generally sensitive to water and tend to lose strength once becomes wet, it is essential that drainage be properly controlled.

a) The site should be graded to provide structures and so that water is not allowed to collect or discharge near the foundation lines.

b) Rainwater discharge at downspouts should be directed onto pavement sections, splash blocks, or other acceptable facilities, which will prevent water from collecting in the soil adjacent to the foundations.

c) Surface runoff water should be collected and drained to suitable discharge points, which is connected to the storm drainage system.

d) Utility lines that cross under or through slab, footings, or wells should be completely sealed or waterproofed, as necessary, to prevent moisture intrusion into the areas under the slab and footings.

e) Landscaping within 5 feet of the perimeter of the foundations should be avoided to reduce the potential and saturation along the foundation.

f) The site grading should not be altered or ditches and drains should not be blocked as a result of future landscaping or any other future construction activities.

9.6 Subgrade Improvement

The potentially liquefiable soils may cause post-liquefaction settlement and differential settlement under the shallow foundation. Mitigation measures should be considered if the potential post-liquefaction differential settlement will be a concern in the foundation design by the structural engineer. The following are recommended to minimize the potential differential settlement from the post-liquefaction settlement.

(a) Excavate 2 feet of existing soil below the bottom of the footing. The excavation should extend 2 feet beyond the footprint of the footing for the bridge structure.

(b) Place a layer of Subgrade Enhancement Geotextile (SEG) on the subgrade. The

Project No. 2014-123-010 subgrade enhancement geotextile may be either woven or non-woven type fabric and should conform to Caltrans standard [Caltrans Standard Specifications Section 88-

1.02 O (Class B2)].

(c) Place 2 feet of Caltrans Class 3 Aggregate Base over the SEG. The Class 3

Aggregate Base should be compacted to 95-percent relative compaction per ASTM D-1557-91.

(d) The SEG should be wrapped on top of the compacted Class 3 Aggregate Base for a minimum overlap of two feet.

The aggregate base and SEG act as a bridge to locally support the proposed building structure over the potentially liquefiable soils. If groundwater is encountered at the bottom of the 2 feet over-excavation, lean concrete base can be considered to be used instead of aggregate base.

9.7 Utility Trench

Installation of new sanitary sewer, water line, and gas line are proposed for this project.

Both open excavation and trenchless methods can be considered based on the available resources and site conditions. The specifications for trenchless installation can be obtained through experienced specialty contractors. If open excavation method is used, a 2(H): 1(V) slope configuration should be stable for a temporary excavation based on the subsurface soil conditions at the time of our field exploration.

All trenches shall be excavated to a width sufficient for satisfactory and safe working conditions and shall comply with all OSHA guidelines. Whenever necessary, bracing and sheeting need to be installed to provide a safe working condition. Adequate protection and maintenance of existing underground and subsurface structures within the work limit should be provided by the contractors.

The final design of slope height, inclination, and excavation depths should not exceed those specified in local, state, or federal safety regulations. The design of the temporary slopes by the contractor or his specialty subcontractor should be conformed to the

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OSHA’s “Guidelines for Excavation and Temporary Sloping”. The contractor or responsible subcontractor should base on the subsurface conditions exposed at the time of construction to determine the temporary slope inclination.

Groundwater may be encountered during the trench excavation. We recommend that the dewatering system be prepared to maintain the excavation in dry condition. The site grading drainage should direct storm water away from the open excavation.

The bedding material and standard trench backfill details should conform to the applicable standards. The following recommendation could be considered as the minimum requirement. The soils to be used as backfill should be free of organics, roots, or other deleterious materials. It should be relatively non-expansive material having a plasticity index (PI) less than 15. The backfill should be placed in 8 inches to 12 inches lifts and compacted to:

A minimum 90% of the material’s modified Proctor maximum dry density (ASTM D 1557) in unpaved areas, and

A minimum 98% in the top 24 inches and 95% below the top 24 inches of the material’s modified Proctor maximum dry density (ASTM D 1557) in paved areas.

9.8 Structural Pavement Design

R-value tests were performed on representative soil samples collected at the project site. The test results are summarized in Table 5. The R-value test results are included in Appendix B (Plates B-6A and B-6B).

TABLE 5: SUMMARY OF R-VALUE TEST RESULTS

Test Boring Plasticity Index R-value

B-1 24 6 B-2 - 9

Findings and Recommendations:

The brief summaries of the design assumptions and recommendations for the structural pavement are discussed below:

Project No. 2014-123-010

1) Based on the R-value test results, the R-values of the subsurface soils from the soil borings are 6 and 9. An R-Value of 6 is assumed for the native soil materials in the design of structural pavement sections.

2) The new pavement design is according to the guidelines of the Caltrans Highway Design Manual (HDM), using Hot Mixed Asphalt (HMA); Aggregate Base (AB) and Aggregate Subbase (AS).

3) Traffic Index (TI) value is not yet available according to the designer. Traffic Indices of 5 to 10 were assumed in the structural pavement design.

4) A foot of aggregate subbase is recommended below the full-depth HMA for R-value less than 10.

5) Based on Section 614.5 of the Highway Design Manual, a SEG (Class B2) is required for flexible pavements when the R-value of the basement soil is less than 20.

Based on the Traffic Indices provided by the designer and the design R-value, the recommended structural pavement sections are shown in the table below.

TABLE 6: PAVEMENT DESIGN RECOMMENDATION

Traffic Index

Option HMA (Type A) Thickness (ft)

Aggregate Base Thickness (ft)

Aggregate Subbase Thickness (ft)

5 1 0.25 0.35 0.50 2 0.65 - 1.00 6 1 0.30 0.45 0.65 2 0.75 - 1.00 7 1 0.35 0.55 0.80 2 0.90 - 1.00 8 1 0.40 0.65 0.90 2 1.05 - 1.00 9 1 0.45 0.75 1.05 2 1.15 - 1.00

10 1 0.55 0.75 1.20 2 1.30 - 1.00

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9.9 Corrosion

The corrosion investigation for this project was performed in general accordance with the provisions of California Test Method 643. Chemical tests were performed on soil samples from Borings B-1 and B-3 to evaluate the corrosion potential of the subsurface soil. A summary of the corrosion test results is presented in the following table.

TABLE 7: SUMMARY OF CORROSION TEST RESULT

Boring Sample

Depth (ft)

Minimum Resistivity

(ohms-cm)

PH Water-soluble

Chloride (ppm)

Water-soluble

Sulfate (ppm)

B-1 6.0 2,010 7.87 29.1 25.2 B-3 9.5 1,100 7.67 27.4 21.0

According to Caltrans Corrosion Guidelines, November 2012 (Version 2.0), Caltrans considers a site to be corrosive to foundation element if one of the following conditions exists for the representative soil samples taken at the site:

Chloride concentration is greater than or equal to 500 ppm, Sulfate concentration is greater than or equal to 2000 ppm, pH is 5.5 or less.

Based on the corrosion test results, the native subsurface soils in Borings B-1 and B-3 are considered non-corrosive per Caltrans corrosion design guidelines. Standard Type II modified or Type I-P (MS) modified cement may be used for the concrete substructure.

10.0 PLAN REVIEW

This report is prepared for the proposed “Vehicle Maintenance facility California Air National Guard Moffett Federal Airfield”. We recommend that final plans for the proposed project to be reviewed by PARIKH prior to construction so that the intent of our recommendations is included in the project plans and specifications and to further see that no misunderstandings or misinterpretations have occurred. However, design-build elements should be reviewed only from overall compliance standpoint.

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11.0 CONSTRUCTION OBSERVATION

To a degree, the performance of any structure is dependent upon construction procedures and quality control measures. Hence, geotechnical observation and testing of grading operations, and foundation excavations should be carried out by the Geotechnical Engineer. If the subsurface conditions different from those forming the basis of our recommendations are encountered, this office should be informed in order to assess the need for design changes.

Therefore, the recommendations presented in this report are contingent upon good quality control and these geotechnical observations during construction.

12.0 INVESTIGATION LIMITATIONS

Our services consist of professional opinions and recommendations made in accordance with generally accepted geotechnical engineering principles and practices and are based on our site reconnaissance and the assumption that the subsurface conditions do not deviate from observed conditions. All work done is in accordance with generally accepted geotechnical engineering principles and practices. No warranty, expressed or implied, of merchantability or fitness, is made or intended in connection with our work or by the furnishing of oral or written reports or findings. The scope of our services did not include any environmental assessment or investigation for the presence or absence of hazardous or toxic materials in structures, soil, surface water, groundwater or air, below or around this site. Unanticipated soil conditions are commonly encountered and cannot be fully determined by taking soil samples and excavating test borings; different soil conditions may require that additional expenditures be made during construction to attain a properly constructed project. Some contingency fund is thus recommended to accommodate these possible extra costs.

This report has been prepared for the proposed project as described earlier, to assist the engineer in the design of this project. In the event any changes in the design or location of the facilities are planned, or if any variations or undesirable conditions are encountered during construction, our conclusions and recommendations shall not be considered valid unless the changes or variations are reviewed and our recommendations modified or approved by us in writing.

Project No. 2014-123-010

This report is issued with the understanding that it is the designer's responsibility to ensure that the information and recommendations contained herein are incorporated into the project and that necessary steps are also taken to see that the recommendations are carried out in the field.

The findings in this report are valid as of the present date. However, changes in the subsurface conditions can occur with the passage of time, whether they are due to natural processes or to the works of man, on this or adjacent properties. In addition, changes in applicable or appropriate standards occur, whether they result from legislation or from the broadening of knowledge. Accordingly, the findings in this report might be invalidated, wholly or partially, by changes outside of our control.

Respectfully submitted, PARIKH CONSULTANTS, INC.

Alston Lam, P.E., G.E. 2605 Gary Parikh, P.E., G.E. 666 Project Engineer Project Manager

AL/GP: S:\Ongoing Projects\2014-123-010\Report\Word\CANG Buildings at Moffet Field (Draft) (9-2014).rpt

APPENDIX A

FIELD EXPLORATION

All the soil borings were drilled with drill rig using 8-inch diameter hollow stem auger. The soil samples were obtained from the borings during drilling at various depths by driving a 2.5 inches Inside Diameter (I. D.) Modified California Sampler or a 1.375 inches I.D. Standard Penetration Sampler (ASTM Test Method No. 1586). The sampler was driven into the subsurface soils under the impact of a 140 pounds hammer having a free fall of 30 inches. The blow counts required to drive the sampler for the last 12 inches are presented on the Logs of Test Borings, Appendix A. (When correlating standard penetration data in similar soils, the blow counts for the Modified California sampler can be converted to equivalent Standard Penetration Test sampler by multiplying a factor of 0.65). Pocket penetration tests were also performed on clay samples to evaluate their consistency.

Upon completion of drilling, the boreholes were backfilled with cement grout.

The borings were drilled under the technical supervision of our engineers, who classified and continuously logged the soils encountered during drilling and supervised the collection of soil samples at various depths for visual examination and laboratory testing. The soil samples were visually classified in the field according to the Unified Soil Classification System and then transported to our laboratory for further evaluation and testing.

The descriptions of the soils encountered and relevant boring information are presented on the Log of Borings in Appendix A. The laboratory test methods and results are presented in Appendix B. The logs presented in Appendix A were prepared from the field logs which were edited after visual re-examination of the soil samples in the laboratory and results of classification tests on selected soil samples as indicated on the logs.

The descriptions and related information presented on these logs of test borings depict subsurface conditions only at the locations indicated on the plan and on the particular date noted on the logs.

Because of the variability from place to place within soil/rock in general, subsurface conditions at other locations may differ from conditions occurring at the locations explored. The abrupt stratum changes shown on the logs may be gradational and relatively minor changes in soil types within a stratum may not be noted on the logs due to field limitations. Also, the passage of time may result in a change in the soil conditions at these locations due to environmental changes.

EVALUATION OF LIQUEFACTION POTENTIAL

9/10/2014

LIQUEFACTION POTENTIAL ANALYSIS (SPT procedures per Youd et al 2001)

PROJECT NAME Moffett Field Vehicle Maintenance and Storage Buildings SOIL GROUPS FAULT INFO PROJECT NO. 2014-123-010 1. GRAVELS, SANDS AND NONPLASTIC SILTS Cascade Fault BORING NO. B-1 2. CLAYS AND PLASTIC SILTS a max (g)= 0.6

FAULT M w = 6.7

GW DEPTH (ft)= 3 BOREHOLE DIA (in)= 8.25 CUT(-)/FILL(+) (ft) = 0 MSF = 1 33 HAMMER ENERGY = 61% DESIGN GW DEPTH (ft)= 3 (below OG)

Sample Depth Soil Blow Sampler σv' σv σv' from to No (ft) Type Count Type (psf) (psf) (psf)

0.0 4.0 1 3 2 19 MC 12.4 1.0 0.75 1.0 1.15 10.8 375.0 1.7 18.4

4.0 8.0 2 6 2 17 MC 11.1 1.0 0.80 1.0 1.15 10.3 562.8 1.7 17.6

8.0 11.5 3 9.5 2 10 MC 6.5 1.0 0.85 1.0 1.15 6.5 781.9 1.6 10.3

11 5 16.5 4 14.5 1 17 SPT 17.0 1.0 0.85 1.2 1.15 20.3 1094.9 1.4 27.4 36% 37.9 1812.5 1094.9 1 0 0 6 1 0 1.0 NON-LIQ.

16 5 21.5 5 19 5 2 9 SPT 9.0 1.0 0.95 1.2 1.15 12.0 1407.9 1.2 14.3

21 5 26.5 6 24 5 2 15 MC 9.8 1.0 0.95 1.0 1.15 10.8 1720.9 1.1 11.7

26 5 30.0 7 29 5 2 41 MC 26.7 1.0 1.00 1.0 1.15 31.2 2033.9 1.0 30.9

Notes: Reference:

1. The correction factors CE (Energy Ratio), CB (Borehole Diameter), CR (Rod Length) and CS (Sampling Method-liner) are per Youd et al. (2001).

2. For correction of overburden, CN = (1/σv')

0.5 with a maximum value of 1.7.

3. The influence of Fines Contents are expressed by the following correction: (N1)60cs = a + b (N1)60 where a and b = coefficients determined from the following relationships for FC < 5% a = 0, b = 1.0 for 5% < FC < 35% a = exp(1.76-(190/FC2)), b = (0.99+(FC1.5/1000)) for FC > 35% a = 5.0, b = 1.2

4. For (N1)60,cs greater than 30, clean granular soils are too dense to liquefy and are classed as non-liquefiable.

Layer Thickness SPT-Neq. CE CR CS CB N60 CN (N1)60

SOIL STRATA LIQUEFACTION RESISTANCE (CRR 7.5 ) CYCLIC STRESS RATIO (CSR) F.S.=(CRR 7 5 /CSR)*MSF*Ks*Ka POST-LIQ. SETTLEMENT

F.C. (N1)60, CS CRR7.5 rd CSR Ka F.S.

Vol. Strain

∆D (in)

Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER Workshops on Evaluation of Liquefaction Resistance of Soils, Youd, et al., ASCE Journal of Geotechnical and Geoenvironmental Engineering, October 2001, Vol. 127 No. 10

Ks

PROJECT NAME Moffett Field Vehicle Maintenance and Storage Buildings SOIL GROUPS FAULT INFO PROJECT NO. 2014-123-010 1. GRAVELS, SANDS AND NONPLASTIC SILTS Cascade Fault BORING NO. B-2 2. CLAYS AND PLASTIC SILTS a max (g)= 0.6

FAULT M w = 6.7

GW DEPTH (ft)= 3 BOREHOLE DIA (in)= 8.25 CUT(-)/FILL(+) (ft) = 0 MSF = 1 33 HAMMER ENERGY = 61% DESIGN GW DEPTH (ft)= 3 (below OG)

Sample Depth Soil Blow Sampler σv' σv σv' from to No (ft) Type Count Type (psf) (psf) (psf)

0.0 4.0 1 3 2 19 MC 12.4 1.0 0.75 1.0 1.15 10.8 375.0 1.7 18.4

4.0 8.0 2 6 2 16 MC 10.4 1.0 0.80 1.0 1.15 9.7 562.8 1.7 16.5

8.0 11.5 3 9.5 2 10 MC 6.5 1.0 0.85 1.0 1.15 6.5 781.9 1.6 10.3

11 5 14.0 4 13 1 10 SPT 10.0 1.0 0.85 1.2 1.15 11.9 1001.0 1.4 16.9 16.9 0 2 1625.0 1001.0 1 0 0 6 1 0 1.0 (0.39) 1 59% 0.48

14 0 18.0 5 14 5 2 10 SPT 10.0 1.0 0.85 1.2 1.15 11.9 1094.9 1.4 16.1

18 0 22.0 6 19 5 2 7 MC 4.6 1.0 0.95 1.0 1.15 5.1 1407.9 1.2 6 0

22 0 26.5 7 24 5 2 11 MC 7.2 1.0 0.95 1.0 1.15 7 9 1720.9 1.1 8 6

26 5 31.5 8 29.5 2 36 MC 23.4 1.0 1.00 1.0 1.15 27.4 2033.9 1.0 27.1

31 5 37.0 9 34.5 2 24 MC 15.6 1.0 1.00 1.0 1.15 18.2 2346.9 0.9 16.8

37 0 41.5 10 39.5 2 24 MC 15.6 1.0 1.00 1.0 1.15 18.2 2659.9 0.9 15.8

41 5 44.5 11 44 2 35 MC 22.8 1.0 1.00 1.0 1.15 26.6 2941.6 0.8 21.9

Notes: Reference:

1. The correction factors CE (Energy Ratio), CB (Borehole Diameter), CR (Rod Length) and CS (Sampling Method-liner) are per Youd et al. (2001).

2. For correction of overburden, CN = (1/σv')

0.5 with a maximum value of 1.7.

3. The influence of Fines Contents are expressed by the following correction: (N1)60cs = a + b (N1)60 where a and b = coefficients determined from the following relationships for FC < 5% a = 0, b = 1.0 for 5% < FC < 35% a = exp(1.76-(190/FC2)), b = (0.99+(FC1.5/1000)) for FC > 35% a = 5.0, b = 1.2

4. For (N1)60,cs greater than 30, clean granular soils are too dense to liquefy and are classed as non-liquefiable.

Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER Workshops on Evaluation of Liquefaction Resistance of Soils, Youd, et al., ASCE Journal of Geotechnical and Geoenvironmental Engineering, October 2001, Vol. 127 No. 10

Ks Ka F.S.

Vol. Strain

∆D (in)

F.C. (N1)60, CS CRR7.5 rd CSR Layer Thickness

SPT-Neq. CE CR CS CB N60 CN (N1)60

SOIL STRATA LIQUEFACTION RESISTANCE (CRR 7.5 ) CYCLIC STRESS RATIO (CSR) F.S.=(CRR 7 5 /CSR)*MSF*Ks*Ka POST-LIQ. SETTLEMENT

PROJECT NAME Moffett Field Vehicle Maintenance and Storage Buildings SOIL GROUPS FAULT INFO PROJECT NO. 2014-123-010 1. GRAVELS, SANDS AND NONPLASTIC SILTS Cascade Fault BORING NO. B-3 2. CLAYS AND PLASTIC SILTS a max (g)= 0.6

FAULT M w = 6.7

GW DEPTH (ft)= 3 BOREHOLE DIA (in)= 8.25 CUT(-)/FILL(+) (ft) = 0 MSF = 1 33 HAMMER ENERGY = 61% DESIGN GW DEPTH (ft)= 3 (below OG)

Sample Depth Soil Blow Sampler σv' σv σv' from to No (ft) Type Count Type (psf) (psf) (psf)

0.0 4.5 1 3 2 37 MC 24.1 1.0 0.75 1.0 1.15 21.1 375.0 1.7 35.9

4.5 8.0 2 6 2 16 MC 10.4 1.0 0.80 1.0 1.15 9.7 562.8 1.7 16.5

8.0 14.5 3 9.5 2 13 MC 8.5 1.0 0.85 1.0 1.15 8.4 781.9 1.6 13.4

14 5 17.5 4 14.5 1 16 MC 10.4 1.0 0.85 1.0 1.15 10.3 1094.9 1.4 14.0 13% 16.4 0 2 1812.5 1094.9 1 0 0 6 1 0 1.0 (0.37) 1 63% 0 59

17 5 23.0 5 19 5 2 7 SPT 7.0 1.0 0.95 1.2 1.15 9 3 1407.9 1.2 11.1

23 0 27.0 6 24 5 2 14 MC 9.1 1.0 0.95 1.0 1.15 10.1 1720.9 1.1 10.9

27 0 30.0 7 29 5 2 32 MC 20.8 1.0 1.00 1.0 1.15 24.3 2033.9 1.0 24.1

Notes: Reference:

1. The correction factors CE (Energy Ratio), CB (Borehole Diameter), CR (Rod Length) and CS (Sampling Method-liner) are per Youd et al. (2001).

2. For correction of overburden, CN = (1/σv')

0.5 with a maximum value of 1.7.

3. The influence of Fines Contents are expressed by the following correction: (N1)60cs = a + b (N1)60 where a and b = coefficients determined from the following relationships for FC < 5% a = 0, b = 1.0 for 5% < FC < 35% a = exp(1.76-(190/FC2)), b = (0.99+(FC1.5/1000)) for FC > 35% a = 5.0, b = 1.2

4. For (N1)60,cs greater than 30, clean granular soils are too dense to liquefy and are classed as non-liquefiable.

Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER Workshops on Evaluation of Liquefaction Resistance of Soils, Youd, et al., ASCE Journal of Geotechnical and Geoenvironmental Engineering, October 2001, Vol. 127 No. 10

Ks Ka F.S.

Vol. Strain

∆D (in)

F.C. (N1)60, CS CRR7.5 rd CSR Layer Thickness

SOIL STRATA LIQUEFACTION RESISTANCE (CRR 7.5 ) CYCLIC STRESS RATIO (CSR) F.S.=(CRR 7 5 /CSR)*MSF*Ks*Ka POST-LIQ. SETTLEMENT

PROJECT NAME Moffett Field Vehicle Maintenance and Storage Buildings SOIL GROUPS FAULT INFO PROJECT NO. 2014-123-010 1. GRAVELS, SANDS AND NONPLASTIC SILTS Cascade Fault BORING NO. B-4 2. CLAYS AND PLASTIC SILTS a max (g)= 0.6

FAULT M w = 6.7

GW DEPTH (ft)= 3 BOREHOLE DIA (in)= 8.25 CUT(-)/FILL(+) (ft) = 0 MSF = 1 33 HAMMER ENERGY = 61% DESIGN GW DEPTH (ft)= 3 (below OG)

Sample Depth Soil Blow Sampler σv' σv σv' from to No (ft) Type Count Type (psf) (psf) (psf)

0.0 5.0 1 3 2 21 MC 13.7 1.0 0.75 1.0 1.15 12.0 375.0 1.7 20.3

5.0 7.5 2 6 2 23 MC 15.0 1.0 0.80 1.0 1.15 14.0 562.8 1.7 23.8

7.5 11.5 3 9.5 1 13 MC 8.5 1.0 0.85 1.0 1.15 8.4 781.9 1.6 13.4 5% 13.4 0.1 1187.5 781 9 1 0 0 6 1 0 1.0 (0.33) 1 89% 0 90

11 5 19.0 4 14 5 1 20 SPT 20.0 1.0 0.85 1.2 1.15 23.9 1094.9 1.4 32.2 3% 32.2 1812.5 1094.9 1 0 0 6 1 0 1.0 NON-LIQ.

19 0 23.0 5 19 5 2 9 SPT 9.0 1.0 0.95 1.2 1.15 12.0 1407.9 1.2 14.3

23 0 27.0 6 24 5 2 12 MC 7.8 1.0 0.95 1.0 1.15 8.7 1720.9 1.1 9 3

27 0 30.0 7 29 5 2 26 MC 16.9 1.0 1.00 1.0 1.15 19.8 2033.9 1.0 19.6

Notes: Reference:

1. The correction factors CE (Energy Ratio), CB (Borehole Diameter), CR (Rod Length) and CS (Sampling Method-liner) are per Youd et al. (2001).

2. For correction of overburden, CN = (1/σv')

0.5 with a maximum value of 1.7.

3. The influence of Fines Contents are expressed by the following correction: (N1)60cs = a + b (N1)60 where a and b = coefficients determined from the following relationships for FC < 5% a = 0, b = 1.0 for 5% < FC < 35% a = exp(1.76-(190/FC2)), b = (0.99+(FC1.5/1000)) for FC > 35% a = 5.0, b = 1.2

4. For (N1)60,cs greater than 30, clean granular soils are too dense to liquefy and are classed as non-liquefiable.

Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER Workshops on Evaluation of Liquefaction Resistance of Soils, Youd, et al., ASCE Journal of Geotechnical and Geoenvironmental Engineering, October 2001, Vol. 127 No. 10

Ks Ka F.S.

Vol. Strain

∆D (in)

F.C. (N1)60, CS CRR7.5 rd CSR Layer Thickness

SOIL STRATA LIQUEFACTION RESISTANCE (CRR 7.5 ) CYCLIC STRESS RATIO (CSR) F.S.=(CRR 7 5 /CSR)*MSF*Ks*Ka POST-LIQ. SETTLEMENT