Subsurface_Info_Doc_KNMD189008.pdf

Subsurface Information for the

F-22 LOCRF Addition Joint Base Pearl Harbor-Hickam

Oahu, Hawaii

THERE IS NO EXPRESS OR IMPLIED GUARANTEE AS TO THE ACCURACY OR COMPLETENESS OF THE INFORMATION AND DATA CONTAINED HEREIN, NOR OF THE INTERPRETATION THEREOF BY THE OWNER, BURNS & McDONNELL

ENGINEERING COMPANY, OR ANY OF THEIR REPRESENTATIVES.

THE SUBSURFACE INFORMATION AND DATA CONTAINED HEREIN DO NOT FORM A PART OF ANY CONTRACT DOCUMENT ISSUED BY BURNS & McDONNELL.

IF THIS SUBSURFACE INFORMATION IS BEING ISSUED IN ELECTRONIC (PDF) FORMAT. NOTE THAT IT CONSISTS OF A 5-

PAGE FRONT-END DOCUMENT WITH A 64-PAGE APPENDIX (FLYSHEET AND REPORT BY KLEINFELDER).

Hawaii Air National Guard

Joint Base Pearl Harbor-Hickam Oahu, Hawaii Project No. 88276

September 2016

COPYRIGHT © 2016 BURNS & McDONNELL ENGINEERING COMPANY, INC.

Project No. 88276 Subsurface Information September 2016

Hawaii Air National Guard i Burns & McDonnell

TABLE OF CONTENTS

Page No.

1.0 GENERAL

2.0 DESIGN NOTES

3.0 WATER LEVEL INFORMATION

4.0 ADDITIONAL SUBSURFACE INFORMATION

5.0 LIMITATIONS

5.1 Document Use

5.2 Variations

APPENDIX A - GEOTECHNICAL ENGINEERING EXPLORATION, HAWAII AIR

NATIONAL GUARD, F-22 LOCRF ADDITION, JOINT BASE

PEARL HARBOR-HICKAM, OAHU, HAWAII. REPORT

PREPARED BY GEOLABS, INC. PREPARED FOR BURNS &

MCDONNELL; REPORT DATED SEPTEMBER 7, 2016.

Hawaii Air National Guard 1 Burns & McDonnell

1.0 GENERAL

This subsurface information document consists of the data and results from a subsurface investigation described in a report titled Geotechnical Engineering Exploration, Hawaii Air National Guard, F-22

LOCRF Addition, Joint Base Pearl Harbor-Hickam, Oahu, Hawaii, dated September 7, 2016. The investigation was performed by GeoLabs, Inc. (GeoLabs) of Honolulu, Hawaii. The report, as prepared by GeoLabs, is included in Appendix A of this document.

Drilling and laboratory testing for this investigation was performed by GeoLabs. The drilling phase was performed April 19 through April 20, 2016. It included the completion of two (2) borings drilled to depths of 63 feet below grade. Laboratory tests were conducted on select available samples following the completion of drilling operations. Boring logs and laboratory test results, as prepared by GeoLabs, are included in the report in Appendix A of this document.

Samples recovered during the subsurface investigation were transported to the laboratory by GeoLabs.

GeoLabs was not compensated to store the samples after testing and reporting beyond their customary retention period prior to disposal.

2.0 DESIGN NOTES

Geotechnical design notes as prepared by Burns & McDonnell pertinent to the current project are available for inspection at Burns & McDonnell’s Kansas City office upon prior written request.

3.0 WATER LEVEL INFORMATION

Water levels were observed by GeoLabs, refer to the applicable Appendix of this document. It should be noted by the reader that fluctuations in water levels may occur over more prolonged periods of readings and can be influenced by various outside factors. It may take groundwater several days, or longer, to reach its hydrostatic levels in holes in cohesive soils.

Seasonal variations in rainfall, changes to on-site conditions, and changes to off-site conditions can affect groundwater levels. Fluctuations in groundwater levels from those noted in logs should be anticipated during construction. Water levels observed and recorded by others reflect only those conditions that existed at the time of investigation and may vary from true phreatic groundwater levels.

Hawaii Air National Guard 2 Burns & McDonnell

4.0 ADDITIONAL SUBSURFACE INFORMATION

Burns & McDonnell has requested from Hawaii Air National Guard additional subsurface information in the vicinity of the Site. Burns & McDonnell was provided with the information as listed below. This information is available for review at Burns & McDonnell’s Kansas City office upon prior written request.

1. Final Report, Geotechnical Exploration, F-22 LO/Composite Repair Facility, Hawaii Air

National Guard, Hickam Air Force Base, Hawaii; prepared for CH2M Hill by Pacific

Geotechnical Engineers, Inc., dated December 15, 2009.

2. Stone Column Construction Records, F-22 LO/Composite Repair Facility, Hawaii Air National

Guard, Hickam Air Force Base, Hawaii; prepared by Hayward Baker, 2010.

Burns & McDonnell has previously obtained subsurface information and prepared documents, as listed below, for other projects in the near vicinity of this project. This information is available for review at

Burns & McDonnell’s Kansas City office upon prior written request.

1. Subsurface Information for the Hickam F-22 WLT Facility, Hickam Air Force Base, Oahu, Hawaii. Burns & McDonnell Project No. 59198. Prepared for U. S. National Guard Bureau, August 2011.

Burns & McDonnell is aware that a significant amount of construction activity has been undertaken in the near vicinity of the Site. Additional information in the form of geotechnical reports and/or construction records associated with construction activity in the vicinity of the Site may exist.

Other than that listed or described above, Burns & McDonnell is not aware of any additional subsurface information in the vicinity of the Site. Requests for additional subsurface information should be directed to Hawaii Air National Guard.

5.0 LIMITATIONS

5.1 Document Use

The information presented in this document has been prepared for the use of Burns & McDonnell. No other warranty, express or implied, is made as to the information included in this document. In the event that conclusions and recommendations based on data contained in this document are made by others, such conclusions and recommendations are the responsibility of others.

Hawaii Air National Guard 3 Burns & McDonnell

The information gathered and presented in this document was not obtained for an environmental audit nor to evaluate the potential for hazardous materials at the Site. The equipment, techniques, and personnel used to perform geoenvironmental exploration differ substantially from those applied in soil and foundation engineering.

The purpose of this document is not intended as preparation for a Geotechnical Baseline Report.

5.2 Variations

The subsurface information submitted in this document is based upon data obtained from test borings completed at the approximate locations indicated in the applicable Appendix of this document. This document does not reflect variations which may occur between test borings. The nature and extent of variations between the test borings may not become evident until construction is performed. If during construction, soil, rock, and/or groundwater conditions appear to be different from those described herein, Burns & McDonnell should be advised so that recommendations made may be evaluated and modified, if necessary. Water levels, as described in this document, reflect only those conditions that existed at the time that this particular subsurface investigation was performed by GeoLabs. Fluctuations or changes in water levels and groundwater conditions can be influenced by sources outside the site investigated, by seasonal rainfall, and by changes in drainage conditions in and around the Site. Fluctuations can occur and should be anticipated between the time of investigation and the time of construction.

APPENDIX A - GEOTECHNICAL ENGINEERING EXPLORATION, HAWAII AIR

NATIONAL GUARD, F-22 LOCRF ADDITION, JOINT BASE

PEARL HARBOR-HICKAM, OAHU, HAWAII. REPORT

PREPARED BY GEOLABS, INC. PREPARED FOR BURNS &

MCDONNELL; REPORT DATED SEPTEMBER 7, 2016.

GEOTECHNICAL ENGINEERING EXPLORATION

HAWAII AIR NATIONAL GUARD

F‐22 LO/CRF ADDITION

JOINT BASE PEARL HARBOR‐HICKAM, OAHU, HAWAII

W.O. 7326‐00 SEPTEMBER 7, 2016

Prepared for

BURNS & MCDONNELL

GEOLABS, INC.

Geotechnical Engineering and Drilling Services

W.O. 7326-00 GEOLABS, INC. Page i Hawaii • California

GEOTECHNICAL ENGINEERING EXPLORATION

HAWAII AIR NATIONAL GUARD

F-22 LO/CRF ADDITION

JOINT BASE PEARL HARBOR-HICKAM, OAHU, HAWAII

W.O. 7326-00 SEPTEMBER 7, 2016

TABLE OF CONTENTS

Page

SUMMARY OF FINDINGS AND RECOMMENDATIONS .............................................. iii

1. GENERAL

1.1 Introduction

1.2 Project Considerations

1.3 Purpose and Scope

2. SITE CHARACTERIZATION

2.1 Regional Geology

2.2 Site Description

2.3 Subsurface Conditions

2.4 Seismic Design Considerations

2.4.1 Earthquake and Seismicity

2.4.2 Liquefaction

2.4.3 Soil Profile Type For Seismic Design

3. DISCUSSION AND RECOMMENDATIONS

3.1 Building Foundation Support System Evaluation

3.2 Building Foundations

3.1.1 Downdrag Loads

3.1.2 Uplift Load Resistance

3.1.3 Lateral Load Resistance

3.1.4 Micropile Foundation Settlements

3.1.5 Micropile Load Test Program

3.3 Minor Equipment Pads

3.4 Site Grading

3.4.1 Site Preparation

3.4.2 Fills and Backfills

3.4.3 Fill Placement and Compaction Requirements

3.4.4 Excavation

3.5 Pavements

3.6 Utility Lines

3.8 Corrosion Potential and Chemical Attack to Concrete

3.10 Drainage

3.11 Design Review

3.12 Construction Monitoring

TABLE OF CONTENTS

Page

W.O. 7326-00 GEOLABS, INC. Page ii

4. LIMITATIONS

CLOSURE

PLATES

Project Location Map ······································································ Plate 1 Site Plan ····················································································· Plate 2 Soil Parameters for Static and Seismic Lateral Load Analysis ·· Plates 3.1 and 3.2

Field Exploration ··························································· Pages A-1 and A-2 Soil Log Legend ······································································ Plate A-0.1 Soil ClassificationLog Key ························································· Plate A-0.2 Rock Log Legend ···································································· Plate A-0.3 Logs of Borings ····························································· Plates A-1 and A-2

Laboratory Tests ······································································· Page B-1 Laboratory Test Data ······················································ Plates B-1 thru B-5

Photographs of Core Samples ········································ Plates C-1 and C-2

W.O. 7326-00 GEOLABS, INC. Page iii

GEOTECHNICAL ENGINEERING EXPLORATION

F-22 LO/CRF ADDITION

JOINT BASE PEARL HARBOR-HICKAM, OAHU, HAWAII

W.O. 7326-00 SEPTEMBER 7, 2016

SUMMARY OF FINDINGS AND RECOMMENDATIONS

Our field exploration at the site encountered a 9-inch thick Portland cement concrete pavement underlain by very dense gravel and sand fill material over medium dense beach deposits and very loose lagoonal deposits that extended to depths of about 24 to 25 feet below the existing pavement surface. The very loose lagoonal deposits are susceptible to liquefaction during a moderate earthquake event. The borings then encountered medium hard to hard coral formation and medium dense coralline detritus extending to the maximum depth explored. We encountered groundwater in both of the borings at depths varying from approximately 6.1 to 6.5 feet below the existing pavement surface.

We understand that in-place soil improvement consisting of vibro-replacement stone columns is being considered as an option to mitigate liquefaction potential at the site. Since vibration is used to install the stone columns, vibration during the installation in addition to further densification of the existing soils below and around the existing building structure from the vibration could cause significant structural damage to the existing building structure. It is our opinion that in-place soil improvement using vibro-replacement stone columns at the site is not a viable option due to the potential structural damage that could occur during the installation operations. Therefore, we recommend supporting the building addition on a deep foundation system consisting of cased micropiles.

The cased micropile foundation system should have a permanent casing and grout bulb diameters of at least 9.625 inches and 8.5 inches, respectively. The permanent casing (unbonded zone) should extend to a depth of about 25 feet below the existing pavement surface where the top of coral formation is anticipated. We recommend utilizing three classes of micropiles that are differentiated by their allowable compressive load capacities. The three micropile classes are as follows:

Type I with an allowable compressive load capacity of 50 kips and bonded zone length of 11 feet.

Type II with an allowable compressive load capacity of 90 kips and bonded zone length of 18 feet.

Type III micropile with an allowable compressive load capacity of 120 kips and bonded zone length of 23 feet.

SUMMARY OF FINDINGS AND RECOMMENDATIONS

W.O. 7326-00 GEOLABS, INC. Page iv

The allowable compressive load capacities of the micropiles are for supporting dead-plus-live loads and may be increased by up to one-third (1/3) for transient loads, such as wind or seismic forces. The text of this report should be referred to for detailed discussion and specific design recommendations.

END OF SUMMARY OF FINDINGS AND RECOMMENDATIONS

W.O. 7326-00 GEOLABS, INC. Page 1

SECTION 1. GENERAL

1.1 Introduction

This geotechnical engineering exploration report presents the results of our analyses and geotechnical recommendations for the Hawaii Air National Guard, F-22

LO/CRF Addition project at Joint Base Pearl Harbor-Hickam in Honolulu on the Island of

Oahu, Hawaii. The project location and general vicinity are shown on the

Project Location Map, Plate 1.

This report summarizes the findings from our field exploration and laboratory testing and presents our geotechnical recommendations derived from our analyses for design of building and minor equipment pad foundations, site grading, pavements, and underground utilities only.

We also utilized the boring and laboratory information contained in the report prepared by Pacific Geotechnical Engineers, Inc. entitled “Geotechnical Exploration, F-22 LO/Composite Repair Facility, Hawaii Air National Guard, Hickam Air Force Base, Hawaii” dated December 15, 2009.

The findings and recommendations presented herein are subject to the limitations noted at the end of this report.

1.2 Project Considerations

The project site is at the existing F-22 LO/CRF facility located at Joint Base Pearl

Harbor-Hickam in Honolulu on the Island of Oahu, Hawaii. We understand that an addition consisting of a third aircraft hangar bay and various shops are planned on the south side of the existing facility. The new addition will be a steel structure. The structural loading anticipated for the new aircraft bay addition is a maximum column load of about 300 kips and a maximum wall load of about 5 kips per lineal foot.

Based on the geotechnical report prepared by others for the existing LO/CRF facility, the very loose to loose granular soils with varying amounts of silt encountered below the existing LO/CRF facility were considered liquefiable. Therefore, the upper

30 feet of the subsurface soils below the existing LO/CRF facility were improved to

SECTION 1. GENERAL

W.O. 7326-00 GEOLABS, INC. Page 2 reduce the potential for liquefaction of the very loose to loose granular soils by installing stone columns spaced at about 7-foot on center. A 25-foot wide band beyond the perimeter of the existing building was improved with stone columns spaced at about

10-foot on center. Due to soil improvement using stone columns, the existing building is supported on shallow foundations.

1.3 Purpose and Scope

The purpose of our geotechnical engineering exploration was to obtain an overview of the subsurface conditions at the site to formulate a summary of the soil/rock conditions for the proposed building addition. In order to accomplish these objectives, we conducted an exploration program generally consisting of the following tasks and work efforts:

1. Research and review of the available plans, soils report, and in-use soil and geologic information related to the project area.

2. Application for permits to drill and coordination of underground utility toning by our field engineer/geologist.

3. Submittal of activity hazard analyses and safety action plan prior to commencement of field exploration.

4. Mobilization and demobilization of a truck-mounted drill rig and two operators to the project site and back.

5. Coring of the existing PCC pavements and drilling and sampling of a total of two borings each extending to a depth of about 63 feet below the existing pavement surface.

6. Coordination of the field exploration and logging of the borings by our geologist.

7. Screening of the soil samples using photoionization detector (PID) equipment by our geologist.

8. Laboratory testing of selected samples obtained during the field exploration as an aid in classifying the materials and evaluating their engineering properties.

9. Analyses of the field and laboratory data to formulate geotechnical engineering recommendations for the design of the project.

SECTION 1. GENERAL

W.O. 7326-00 GEOLABS, INC. Page 3

10. Preparation of this report summarizing our work on the project and presenting our findings and recommendations.

11. Coordination of our overall work on the project by our senior project engineer.

12. Quality assurance of our work and client/design team consultation by our principal engineer.

13. Miscellaneous work efforts, such as drafting, word processing, and clerical support.

Detailed descriptions of our field exploration and Logs of Borings are provided in

Appendix A. Results of the laboratory tests performed on selected soil and rock core samples are presented in Appendix B. Photographs of the core samples are presented in Appendix C.

END OF GENERAL

W.O. 7326-00 GEOLABS, INC. Page 4

SECTION 2. SITE CHARACTERIZATION

2.1 Regional Geology

The Island of Oahu was built by the extrusion of basalt and basaltic lavas from the Waianae and Koolau shield volcanoes. The older Waianae Volcano is estimated to be middle to late Pliocene in age and the younger Koolau Volcano is estimated to be late Pliocene to early Pleistocene in age. After a long period of volcanic inactivity, during which time erosion incised deep valleys into the Koolau Shield, volcanic activity returned with a series of lava flows followed by cinder and tuff cone formations. These series are referred to as the Honolulu Volcanic Series.

The geologic conditions underlying the site are the result of a complex series of depositional and erosional events due to glacio-eustatic sea level changes and post-erosional volcanic activities during the Pleistocene Epoch. The Koolau Volcanic

Shield was built during the early Pleistocene Epoch by thinly bedded basaltic lava flows.

Following the cessation of activity of the Koolau Volcano, alluvial soil materials were deposited in an estuarine and deltaic environment in the area of Pearl Harbor.

The sea level fluctuated several times, receding perhaps 300 feet below and rising about 100 feet above the present sea level.

During the Recent Epoch, as the sea level rose to its current stand, the area was covered with additional sediments consisting primarily of soft and loose lagoonal marine deposits. Land development and reclamation projects in the past 40 to 60 years have added man-made fills, bringing the site to its present configuration.

2.2 Site Description

The project site is located at the existing F-22 LO/CRF Facility (Building 3408) at

Joint Base Pearl Harbor-Hickam. The building addition is planned at the south side of the existing facility as shown on the Site Plan, Plate 2.

In general, the site is open and relatively level with existing pavement surface elevations ranging between +7 and +8 feet Mean Sea Level (MSL). The pavements consist of Portland cement concrete that is in relatively good condition.

SECTION 2. SITE CHARACTERIZATION

W.O. 7326-00 GEOLABS, INC. Page 5

2.3 Subsurface Conditions

The subsurface conditions at the site were explored by drilling and sampling two borings, designated as Boring Nos. 1 and 2, each extending to a depth of about

63 feet below the existing pavement surface. The approximate boring locations are shown on the Site Plan, Plate 2.

In general, Boring Nos. 1 and 2 encountered a 9-inch thick Portland cement concrete pavement underlain by very dense gravel and sand fill material extending to a depth of about 5 feet below the existing pavement surface. The fill material was underlain by medium dense beach deposits consisting of coralline sand extending to depths of about 11 to 12 feet below the existing pavement surface. Below the beach deposits, very loose lagoonal deposits consisting of silty coralline sand were encountered to depths of about 24 to 25 feet below the existing pavement surface. The borings then encountered medium hard to hard coral formation and medium dense coralline detritus extending to the maximum depth explored of about 63 feet below the existing pavement surface.

We encountered groundwater in both of the borings drilled at depths varying from approximately 6.1 to 6.5 feet below the existing pavement surface. The groundwater levels generally correspond to elevations of about 1.2 and 1.7 feet Mean Sea Level

(MSL). It should be noted that the groundwater levels are subject to change due to rainfall, seasonal precipitation, surface water runoff, and other factors.

Detailed descriptions of our field exploration methodology and the Logs of

Borings are presented in Appendix A. Results of the laboratory tests performed on selected soil samples and rock cores obtained from our field exploration are presented in Appendix B. Photographs of the rock core samples obtained from our field exploration are presented in Appendix C.

2.4 Seismic Design Considerations

Unified Facilities Criteria (UFC) 1-200-01, General Building Requirements, indicates that the current code in effect is the International Building Code, 2012 Edition

W.O. 7326-00 GEOLABS, INC. Page 6

(IBC 2012). Based on the IBC 2012, the project site may be subjected to seismic activity; therefore, seismic design considerations will need to be addressed.

2.4.1 Earthquake and Seismicity

In general, earthquakes throughout the world are caused by shifts in the tectonic plates. In contrast, earthquake activity in Hawaii is primarily linked to volcanic activity; therefore, earthquake activity in Hawaii generally occurs before or during volcanic eruptions. In addition, earthquakes may result from the underground movement of magma that comes close to the surface but does not erupt. The

Island of Hawaii experiences thousands of earthquakes each year, but most are so small that they can only be detected by sensitive instruments. However, some of the earthquakes are strong enough to be felt, and a few cause minor to moderate damage.

In general, earthquakes associated with volcanic activity are most common on the

Island of Hawaii. Earthquakes that are directly associated with the movement of magma are concentrated beneath the active Kilauea and Mauna Loa Volcanoes on the Island of Hawaii. Because the majority of earthquakes in Hawaii

(over 90 percent) are related to volcanic activity, the risk of seismic activity and degree of ground shaking diminishes with increased distance from the Island of

Hawaii. The Island of Hawaii has experienced numerous earthquakes greater than

Magnitude 5 (M5+); however, earthquakes are not confined only to the Island of

Hawaii.

To a lesser degree, the Island of Maui has experienced several earthquakes greater than Magnitude 5. Therefore, moderate to strong earthquakes have occurred in the County of Maui. The effects of earthquakes occurring on the Islands of Hawaii and Maui may be felt on the Island of Oahu. For example, small landslides occurred on the Island of Oahu as a result of the Maui Earthquake of

1938 (M6.8). Some houses on the Island of Oahu were reportedly damaged as a result of the Lanai Earthquake of 1871 (M7+).

W.O. 7326-00 GEOLABS, INC. Page 7

In the last 150 years of recorded history, we are not aware of earthquakes greater than Magnitude 6 that have occurred on the Island of Oahu. An earthquake of

Magnitude 4.8 to 5.0 occurred along the Diamond Head Fault in 1948 on the Island of Oahu. The moderate tremor resulted in broken store windows, ruptured building walls, and broken underground water mains.

2.4.2 Liquefaction

Based on the 2012 International Building Code, the project site may be subject to seismic activity and the potential for soil liquefaction at the project site will need to be evaluated.

Soil liquefaction is a condition where saturated cohesionless soils located near the ground surface undergo a substantial loss of strength due to the build-up of excess pore water pressures resulting from cyclic stress applications induced by earthquakes. In this process, when the loose saturated sand deposit is subjected to vibration (such as during an earthquake), the soil tends to densify and decrease in volume causing an increase in pore water pressure. If drainage is unable to occur rapidly enough to dissipate the build-up of pore water pressure, the effective stress

(internal strength) of the soil is reduced. Under sustained vibrations, the pore water pressure build-up could equal the overburden pressure, essentially reducing the soil shear strength to zero and causing it to behave as a viscous fluid. During liquefaction, the soil acquires a mobility sufficient to permit both horizontal and vertical movements, and if not confined, will result in significant deformations.

Soils most susceptible to liquefaction are loose, uniformly graded, fine-grained sands and loose silts with little cohesion. The major factors affecting the liquefaction characteristics of a soil deposit are as follows:

W.O. 7326-00 GEOLABS, INC. Page 8

FACTORS LIQUEFACTION SUSCEPTIBILITY

Grain Size Distribution Fine and uniform sands and silts are more susceptible to liquefaction than coarse or well-graded sands.

Initial Relative Density

Loose sands and silts are most susceptible to liquefaction. Liquefaction potential is inversely proportional to relative density.

Magnitude and Duration of Vibration

Liquefaction potential is directly proportional to the magnitude and duration of the earthquake.

In general, the subsurface information obtained from the borings indicates that the site is underlain by very loose lagoonal deposits overlying coral formation and coralline detritus. The lagoonal deposits consisted of silty sand and gravel. Based on our analyses, the lagoonal deposits are potentially liquefiable during a seismic event of Magnitude 6 with an associated peak ground acceleration of 0.364g.

It appears that the very loose lagoonal deposits have a factor of safety of 0.3 to 1.0 against liquefaction. Therefore, it is our opinion that the project site could be subject to appreciable ground settlements (on the order of about 4 to 6 inches) in the event of liquefaction during a moderate earthquake (M6+). The effects of potential liquefaction at the site should be taken into consideration when designing the proposed new addition. However, we believe that lateral spreading associated with liquefaction would not be a significant design consideration based on the relatively flat site topography.

2.4.3 Soil Profile Type For Seismic Design

In general, the subsurface information obtained from the borings indicates that the site is underlain by very loose lagoonal deposits overlying coral formation and coralline detritus. Based on our engineering analyses, it appears that the very loose lagoonal deposits have a factor of safety of 0.3 to 1.0 against liquefaction.

Therefore, the very loose lagoonal deposits are potentially liquefiable in the event of a moderate earthquake.

W.O. 7326-00 GEOLABS, INC. Page 9

In accordance with Chapter 20, Site Classification Procedure for Seismic Design contained in ASCE 7-10 (Minimum Design Loads for Buildings and Other

Structures), a site-response analysis is not required to determine the spectral accelerations for liquefiable soils for structures having fundamental periods of vibration equal to or less than 0.5 seconds. Rather, a site class is permitted to be determined in accordance with Section 20.3 and the corresponding values of Fa and Fv determined from Tables 11.4-1 and 11.4-2.

Based on the Technical Guidelines provided for the project, we understand that in the event that the site is determined to be classified as a Site Class F due to liquefaction potential, the Structural Engineer has determined that the 0.5-second fundamental period exception noted in Section 20.3.1 of ASCE 7-10 may be applied to the proposed facility addition. Therefore, a site class is permitted to be determined in accordance with Section 20.3 and the corresponding values of Fa and Fv may be determined from Tables 11.4-1 and 11.4-2.

Based on the subsurface materials encountered at the site and the geologic setting of the area, we anticipate the project site may be classified from a seismic analysis standpoint as being a “Soft Clay Soil” site corresponding to a Site Class E soil profile based on Table No. 20.3-1 of ASCE 7-10 Standard. Based on Site Class E, the following seismic design parameters were estimated and may be used for seismic analysis of the project.

SEISMIC DESIGN PARAMETERS

Parameter Value

Peak Bedrock Acceleration, PBA (Site Class B) = 0.261g

Spectral Response Acceleration (Site Class B), SS = 0.566g

Spectral Response Acceleration (Site Class B), S1 = 0.162g

Site Class = “E”

Site Coefficient, Fpga = 1.397

Site Coefficient, Fa = 1.568

Site Coefficient, Fv = 3.314

W.O. 7326-00 GEOLABS, INC. Page 10

SEISMIC DESIGN PARAMETERS

Parameter Value

Peak Ground Acceleration, PGA (Site Class E) = 0.364g

Design Spectral Response Acceleration, SDS = 0.592g

Design Spectral Response Acceleration, SD1 = 0.358g

Seismic Design Category = “D”

END OF SITE CHARACTERIZATION

W.O. 7326-00 GEOLABS, INC. Page 11

SECTION 3. DISCUSSION AND RECOMMENDATIONS

The subsurface conditions at the site below the 9-inch thick Portland cement concrete pavement consists of very dense gravel and sand fill material over medium dense beach deposits and very loose lagoonal deposits that extended to depths of about 24 to 25 feet below the existing pavement surface. Medium hard to hard coral formation and medium dense coralline detritus was encountered below the lagoonal deposits extending to the maximum depth explored of about 63 feet below the existing pavement surface. We encountered groundwater in both of the borings at depths varying from approximately 6.1 to 6.5 feet below the existing pavement surface.

As mentioned above, the very loose lagoonal deposits are susceptible to liquefaction during a moderate earthquake event. We understand that in-place soil improvement consisting of vibro-replacement stone columns is being considered for the project to mitigate liquefaction potential at the site. Since vibration is used to install the stone columns, vibration during the installation of the vibro-replacement stone columns could potentially cause structural damage to the existing building structure since the new addition adjoins the existing building structure. In addition, the vibration during the installation process could further densify the existing soils below and around the existing building structure resulting in foundation settlement that could cause significant structural damage to the existing building structure. Based on the above discussion, we believe that in-place soil improvement using vibro-replacement stone columns at the site is not a viable option. Therefore, a deep foundation system consisting of cased micropiles with a casing outside diameter (OD) of about 9.625 inches and bond lengths of 11 to 23 feet should be used to support the building addition.

Detailed discussion of these items and our geotechnical recommendations for the design of building and minor equipment pad foundations, site grading, pavements, and underground utilities for the project are presented in the following sections.

3.1 Building Foundation Support System Evaluation

We understand that a new aircraft bay is proposed to be added to the existing

F-22 LO/CRF facility. Based on the information provided, the existing F-22 LO/CRF

W.O. 7326-00 GEOLABS, INC. Page 12 facility is supported on shallow foundations bearing on soils that were improved with vibro-replacement stone columns that are spaced at approximately 7 feet center-to-center. The outer perimeter of the existing facility consists of a 25-foot wide zone of stone columns spaced at about 10 feet center-to-center. It should be noted that the majority of the proposed new addition is located outside the zone that has been previously improved with vibro-replacement stone columns.

The structural loading anticipated for the new aircraft bay addition is a maximum column load of about 300 kips and a maximum wall load of about 5 kips per lineal foot.

Based on the above subsurface conditions encountered and the anticipated structural loads, we believe that appreciable ground settlements will occur if the building addition is supported on shallow foundations. In addition, the site could be subjected to appreciable ground settlement, on the order of about 4 to 6 inches, in the event of liquefaction during a moderate earthquake (M6+). Due to potential for ground settlement, the proposed building addition may sustain appreciable damage if it is supported on a shallow foundation system.

In-place soil improvement consisting of vibro-replacement stone columns was evaluated as an option to mitigate liquefaction potential at the site. Vibro-replacement stone columns would densify the loose lagoonal deposits and improve drainage characteristics of the subsurface soils to reduce the potential for liquefaction, thus allowing the use of shallow foundations. However, since vibration is used to install the stone columns, vibration during the installation of the vibro-replacement stone columns could potentially cause structural damage to the existing building structure since the new addition adjoins the existing building structure. In addition, the vibration during the installation process could further densify the existing soils below and around the existing building structure resulting in foundation settlement that could cause significant structural damage to the existing building structure. Therefore, we believe that in-place soil improvement using vibro-replacement stone columns at the site is not a viable option.

Based on the above considerations, we recommend supporting the building addition on a deep foundation system consisting of cased micropiles. Detailed

W.O. 7326-00 GEOLABS, INC. Page 13 discussions and our geotechnical recommendations for the design of the cased micropile foundation system are presented in the following sections herein.

3.2 Building Foundations

In general, the cased micropile foundation system consists of a small diameter

(usually less than 12 inches), drilled and grouted, pile with steel casing and reinforcing.

The micropile foundation is typically constructed by drilling a hole (with casing), placing reinforcing steel in the hole, and grouting the hole. Micropiles are desirable because they can be installed readily in access restrictive environments and in numerous soil types and ground conditions. In addition, the micropile installation generally causes minimal disturbance to adjacent structures, the adjacent soils, and the environment.

Based on the subsurface conditions encountered at the project site, we recommend utilizing a cased micropile system with a grout bulb diameter of 8.5 inches to support the proposed addition. The permanent casing for the cased micropile system should have an outside diameter (OD) of about 9.625 inches. The permanent casing

(unbonded zone) should extend to the top of the coral formation encountered at an average depth of about 25 feet below the existing ground surface. The minimum thickness of the permanent casing should be about 0.545 inches.

Based on the subsurface conditions anticipated at the project site, we recommend utilizing three classes of micropiles differentiated by their allowable compressive load capacities. Based on the subsurface conditions anticipated at the project site, we recommend utilizing a Type I micropile with an allowable compressive load capacity of 50 kips (25 tons), a Type II micropile with an allowable compressive load capacity of up to 90 kips (45 tons), and a Type III micropile with an allowable compressive load capacity of 120 kips (60 tons) to support the building addition. The allowable compressive load capacities of the micropiles are for supporting dead-plus-live loads and may be increased by up to one-third (1/3) for transient loads, such as wind or seismic forces.

The micropiles would derive its vertical support primarily in the bonded zone from skin friction between the grout and the surrounding coral formation and coralline

W.O. 7326-00 GEOLABS, INC. Page 14 detritus. To provide an allowable compressive load capacity of 50, 90, and 120 kips, the bonded zones of the micropile should be embedded a minimum of 11, 18, and

23 feet below the bottom of the permanent casing for Type I, Type II, and Type III micropiles, respectively. Our recommendations pertaining to the micropile allowable compressive load capacities and lengths are presented in the following table.

COMPRESSIVE LOAD CAPACITIES OF MICROPILES

Type

Allowable Compressive Load Capacity

(kips)

Bonded Zone

Length (feet)

Average Micropile

Length (feet)

I 50 11 36

II 90 18 43

III 120 23 48

Notes:

1. Bonded Zone Length is the micropile length below the bottom of the permanent casing.

2. Average Micropile Length is measured from below the existing pavement surface.

The ultimate skin friction of the coral formation and coralline detritus used to achieve the ultimate compressive load capacities is approximately 5.0 kips per square foot (ksf). A factor of safety of 2.0 was used in arriving at the allowable compressive load capacities provided in the above table. In general, the micropiles should have a minimum center-to-center spacing of about 30 inches to avoid reduction in vertical load capacity due to group action and to facilitate drilling of the micropiles.

To facilitate the micropile drilling and ensure the quality of the grouting, we recommend advancing the steel casing to the bottom of the micropile during the drilling operation. The steel casing may be withdrawn during the grouting operation while a minimum of 5 feet grout head is maintained above the bottom of the casing at all times.

3.1.1 Downdrag Loads

The lagoonal deposits at the project site may be susceptible to liquefaction during a seismic event. In the event of seismically induced liquefaction, settlement of the lagoonal deposits will occur at the project site. When the lagoonal deposits move

W.O. 7326-00 GEOLABS, INC. Page 15 downward relative to the stationary micropile, the downward movement will result in negative skin friction forces, generally known as downdrag forces, acting on the micropile shaft. The magnitude of the downdrag force depends on the thickness of the liquefiable layer, relative density of the potentially liquefiable lagoonal deposits, and the micropile perimeter.

Due to the potential for liquefaction of the very loose lagoonal deposits at the project site, settlement of the lagoonal deposits will result in downdrag loading of the micropile foundations extending through the potentially liquefiable materials.

Based on our foundation analyses, we estimate that the downdrag load imposed on the micropiles due to the potential for liquefaction of the lagoonal deposits may be on the order of about 7 kips. The allowable compressive load capacities provided in the above table have already taken into account of the expected downdrag load in the micropile foundation analyses.

3.1.2 Uplift Load Resistance

Uplift loads imposed on the micropiles may be resisted by shear along the grout bulb (bonded zone) and the adjacent soils. Our recommendations for the micropile uplift load capacities are presented in the following table.

UPLIFT LOAD CAPACITIES

FOR SUSTAINED LOADING CONDITIONS

Type

Uplift Load Capacity

(kips)

I 35

II 60

III 75

The ultimate skin friction of the coral formation and coralline detritus used to achieve the uplift load capacities for transient loading is approximately 3.0 ksf. The uplift load capacities provided are intended for sustained load applications. For transient loads, the uplift load capacities provided in the above table may be increased by 50 percent. The project structural engineer should check the capacity of the micropile member in tension.

W.O. 7326-00 GEOLABS, INC. Page 16

3.1.3 Lateral Load Resistance

Lateral loads imposed on the new structure may be resisted by the lateral load capacity of the micropiles. The lateral load resistance of micropiles is a function of the stiffness of the surrounding soil, the stiffness of the pile, allowable deflection at the top of the pile, and the induced moment in the pile. We understand the lateral load analyses will be performed using the program LPILE-plus for Windows, which is a microcomputer adaptation of a finite difference, laterally loaded pile program originally developed at the University of Texas at Austin. The soil parameters to be used for lateral load analyses of the micropiles are presented on Plates 3.1 and 3.2.

Lateral loads imposed on the new structure also may be resisted by passive earth pressure resistance against the vertical faces of the pile cap and grade beams and by shear acting along the sides of the pile caps and grade beams.

Passive pressure resistance against the vertical faces of the pile cap and grade beams may be estimated using an equivalent fluid pressure of 330 pounds per square foot per foot of depth (pcf) above the groundwater level and 140 pcf below the groundwater level. The passive pressure resistance should be fully mobilized with a deflection of 0.5 inch provided that the bottom of the pile caps and grade beams are embedded a maximum of 24 inches below the finished grades.

Additional resistance to lateral loads may be provided by shear resistance between the sides of the pile caps and grade beams and the adjacent soils. A side shear resistance of up to 150 pounds per square foot (psf) may be used for transient loads such as wind or seismic forces only.

3.1.4 Micropile Foundation Settlements

Settlements of the micropile foundations will result primarily from elastic compression of the pile member and subgrade response. We estimate the total settlement of the micropile-supported foundations to be less than 0.75 inch with differential settlements between columns supported on micropiles not exceeding about one-half of the total settlement. We believe that these settlements are essentially elastic and should occur as the loads are applied.

W.O. 7326-00 GEOLABS, INC. Page 17

3.1.5 Micropile Load Test Program

It should be noted that the compressive and uplift load capacities of the micropiles is highly dependent on the drilling procedures and the grouting methods employed by the contractor to install the micropile. Therefore, the compressive and uplift load capacity of the micropile may vary considerably between different contractors and micropile foundation systems. In order to determine whether the contractor’s methods of micropile installation are adequate and to determine the ultimate compressive load capacity, we recommend performing a pre-production compressive load test at the site. In general, the purpose of the pre-production load test on a micropile is to fulfill the following objectives:

To examine the adequacy of the methods and equipment proposed by the contractor to install the micropiles to the depths required

To assess the contractor’s method of drilling and grout injection

To evaluate the degree of long-term settlements of the micropile

In general, the pre-production compressive load test should be performed in accordance with ASTM D1143. Based on experience, we believe that the load test should be conducted at least 7 days after completion of the micropile installation to allow the grout adequate time to cure.

For the compressive load test, a minimum of four additional micropiles may be used for reaction during the compressive load testing of the pre-production load test micropile. The reaction micropiles may be installed to depths as deep as the load test micropile to provide adequate reaction in uplift (to be determined by the contractor).

The load test micropile should be loaded gradually to at least 200 percent of the allowable compression design load of approximately 120 kips. In addition, we recommend holding the micropile for a minimum of 4 hours at 200 percent of the allowable design load depending on the recorded movements of the load test micropile. Please note that the pre-production load test is an integral part of the design of the micropile foundation system.

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In addition to the pre-production load test, we also recommend performing pullout tests (proof tests) on selected micropiles during construction to confirm the load carrying capacity of the installed micropiles. We recommend testing a minimum

10 percent of the total number of micropiles (or minimum of four micropiles) for pullout. The pullout tests should consist of subjecting the micropile to at least

133 percent of the design loads, and the maximum test load should be held for at least 10 or 60 minutes. Pullout tests on the micropiles also are integral parts of the design of the micropile foundation system.

A specialty contractor experienced in the construction of a micropile foundation system (minimum five projects) should perform installation of the micropiles. Due to the specialized nature of the micropile foundation construction, observation and testing of the micropile foundation system should be designated a “Special

Inspection” item.

3.3 Minor Equipment Pads

We understand that lightly loaded equipment pads are planned for the project.

These lightly loaded structures may be supported on shallow foundations consisting of slab-on-grade with thickened edge footings. It is understood that these light structures may settle in the event of a moderate earthquake due to liquefaction.

An allowable bearing pressure of up to 2,500 psf may be used for the design of footings bearing on the recompacted on-site fill materials (minimum 90 percent relative compaction). This bearing value is for dead-plus-live loads and may be increased by one-third (1/3) for transient loads, such as those caused by wind or seismic forces.

Bottom of footings should be embedded a minimum of 18 inches below the lowest adjacent finished grade.

Foundations next to utility trenches or easements should be embedded below a

45-degree imaginary plane extending upward from the bottom edge of the utility trench, or the footings should extend to a depth as deep as the inverts of the utility lines.

If the foundations are designed and constructed as recommended herein, we estimate that footing settlements under the anticipated static design loads for footings

W.O. 7326-00 GEOLABS, INC. Page 19 bearing on the re-compacted on-site soils to be on the order of about 1 inch or less.

Differential settlements between adjacent footings supported on similar materials should be on the order of about 0.5 inch or less.

Lateral loads acting on the structures supported on shallow foundations may be resisted by a combination of friction between the base of the foundation and the bearing materials and by passive earth pressure developed against the near-vertical faces of the embedded portion of the footings. A coefficient of friction of 0.40 may be used for footings bearing on the re-compacted on-site fill soils. Resistance due to passive earth pressure may be calculated using an equivalent fluid pressure of 330 pcf. This value assumes that the concrete for the footings is cast neat against soil materials. Otherwise, the soils around the footings should be well compacted (minimum of 90 percent relative compaction). Unless covered by pavements or slabs, the passive pressure resistance in the upper 12 inches below the finished grade should be neglected.

We recommend providing a minimum 6-inch thick layer of aggregate subbase course below the slab-on-grade to provide uniform support. The aggregate subbase course should be compacted to a minimum of 95 percent relative compaction. Prior to placing the aggregate subbase course, the slab subgrade soils should be scarified to a depth of about 8 inches, moisture-conditioned to about 2 percent above the optimum moisture content, and compacted to a minimum of 95 percent relative compaction.

3.4 Site Grading

We understand that site grading for the project will generally consist of minimal cuts and fills. The following grading items are addressed in the succeeding subsections:

1. Site Preparation

2. Fills and Backfills

3. Fill Placement and Compaction Requirements

4. Excavation

A Geolabs representative should monitor the site grading operations to observe whether undesirable materials are encountered during the excavation and site preparation process and to confirm whether the exposed subsurface conditions are similar to those encountered in our field exploration.

W.O. 7326-00 GEOLABS, INC. Page 20

3.4.1 Site Preparation

At the on-set of earthwork, areas within the contract grading limits should be cleared thoroughly. Debris, deleterious materials, and other unsuitable materials should be removed and disposed of properly off-site to reduce the potential for contamination of the excavated materials. Soft and yielding areas encountered during clearing below areas designated to receive fill should be over-excavated to expose firm material, and the resulting excavation should be backfilled with well-compacted fill. The excavated soft soils should be disposed properly off-site.

Slabs and foundations of the existing structures and pavements to be demolished should be completely removed. Over-excavations resulting from the demolition operations should be backfilled with compacted granular fill material. Existing underground utilities to be abandoned should be removed, and the resulting excavation should be properly backfilled with the excavated on-site materials.