87618_Subsurface_Information.pdf

Subsurface Information for the

Combined Support Maintenance Shop Keaukaha Military Reservation

Hilo, Island of 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 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 4‐

PAGE FRONT‐END DOCUMENT WITH A 93‐PAGE APPENDIX (FLYSHEET AND REPORT BY GEOLABS, INC.).

Hawaii Army National Guard Hilo, Island of Hawaii

Project No. 87618 April 2016

COPYRIGHT © 2016 BURNS & McDONNELL ENGINEERING COMPANY, INC.

Project No. 87618 Subsurface Information April 2016

Hawaii Army 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, COMBINED

SUPPORT MAINTENANCE SHOP NO. 2, KEAUKAHA MILITARY

RESERVATION, HILO, ISLAND OF HAWAII, APRIL 1, 2016,

PREPARED FOR BURNS & MCDONNELL, PREPARED BY

GEOLABS, INC.

Hawaii Army 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, Combined Support Maintenance Shop

No. 2, Keaukaha Military Reservation, Hilo, Island of Hawaii, dated April 1, 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 January 27 through February 4, 2016. It included the completion of sixteen (16) borings drilled to depths ranging from 10 feet to 50 feet below grade, and two (2) probes extending 5 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 have not been prepared by Burns & McDonnell for this project.

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.

Groundwater elevation information as obtained by Geolabs is presented in Appendix A of this document.

Hawaii Army National Guard 2 Burns & McDonnell

4.0 ADDITIONAL SUBSURFACE INFORMATION

Burns & McDonnell is not aware of any significant construction activity that has been undertaken in the near vicinity of the Site. Burns & McDonnell is not aware of any additional subsurface information in the vicinity of the Site.

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.

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, COMBINED

SUPPORT MAINTENANCE SHOP NO. 2, KEAUKAHA MILITARY

RESERVATION, HILO, ISLAND OF HAWAII, APRIL 1, 2016;

REPORT PREPARED FOR BURNS & MCDONNELL,

PREPARDED BY GEOLABS, INC.

GEOTECHNICAL ENGINEERING EXPLORATION

COMBINED SUPPORT MAINTENANCE SHOP NO. 2

KEAUKAHA MILITARY RESERVATION

HILO, ISLAND OF HAWAII

W.O. 7289‐00 APRIL 1, 2016

Prepared for

BURNS & MCDONNELL

Geotechnical Engineering and Drilling Services

W.O. 7289-00 GEOLABS, INC. Page i Hawaii • California

GEOTECHNICAL ENGINEERING EXPLORATION

COMBINED SUPPORT MAINTENANCE SHOP NO. 2

KEAUKAHA MILITARY RESERVATION

HILO, ISLAND OF HAWAII

W.O. 7289-00 APRIL 1, 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 Foundations

3.2 Probing and Grouting

3.3 Slabs-On-Grade

3.4 Retaining Structures

3.4.1 Retaining Structure Foundations

3.4.2 Static Lateral Earth Pressures

3.4.3 Dynamic Lateral Earth Forces

3.4.4 Drainage

3.5 Site Grading

3.5.1 Site Preparation

3.5.2 Fills and Backfills

3.5.3 Fill Placement and Compaction Requirements

3.5.4 Excavation

3.5.5 Cut and Fill Slopes

3.6 Pavements

3.7 Utility Lines

3.8 Corrosion Potential and Chemical Attack to Concrete

3.10 Leach Field

3.11 Retention Pond

TABLE OF CONTENTS

Page

W.O. 7289-00 GEOLABS, INC. Page ii

3.12 Drainage

3.13 Design Review

3.14 Construction Monitoring

4. LIMITATIONS

CLOSURE

PLATES

Project Location Map .................................................................................. Plate 1 Site Plan ..................................................................................................... Plate 2

APPENDIX A

Field Exploration ...................................................................................... Page A-1 Soil Log Legend ..................................................................................... Plate A-0.1 Soil Classification Log Key .................................................................... Plate A-0.2 Rock Log Legend .................................................................................. Plate A-0.3 Logs of Borings ....................................................................... Plates A-1 thru A-18

APPENDIX B

Laboratory Tests ...................................................................................... Page B-1 Laboratory Test Data ................................................................ Plates B-1 thru B-9

APPENDIX C

Percolation Test Results .......................................................................... Plate C-1

APPENDIX D

Field Infiltration Test Results ................................................................... Plate D-1

APPENDIX E

Photographs of Core Samples ................................................ Plates E-1 thru E-12

W.O. 7289-00 GEOLABS, INC. Page iii

GEOTECHNICAL ENGINEERING EXPLORATION

COMBINED SUPPORT MAINTENANCE SHOP NO. 2

KEAUKAHA MILITARY RESERVATION

HILO, ISLAND OF HAWAII

W.O. 7289-00 APRIL 1, 2016

SUMMARY OF FINDINGS AND RECOMMENDATIONS

In general, the subsurface conditions at the site consists of fill underlain by clinker

(basaltic fragments) over medium hard to hard basalt rock formation. Our borings encountered some localized loose zones in the fill layer. We did not encounter groundwater in our borings at the time of our field exploration.

Based on the subsurface conditions encountered at the site, we recommend using shallow spread and/or continuous strip footings to support the new structures planned. As an alternative, foundations for support of the new structures may also consist of thickened-edge slab footings. We recommend using an allowable bearing pressure of up to 3,500 psf for design of footings bearing on the re-compacted on-site fill or new compacted structural fills needed to achieve the design finished grades.

In addition, we recommend implementing a program of cavity probing and grouting of the foundation locations supported on less than 5 feet of compacted fills or on-site soils due to the presence of cavities and/or voids in the basaltic lava flows. The primary purpose of probing and grouting the foundation locations is to reduce the potential for loss of foundation support resulting from the collapse of cavities and/or the migration of fine materials into voids below the foundation.

One percolation test was performed at the proposed leach field location. Based on the percolation test conducted, the percolation rate at the proposed leach field location is less than 1 minute per inch. In accordance with the "Manual of Septic-Tank Practice" prepared by the U.S. Department of Health, Education, and Welfare, the leach field location with the percolation rate obtained at the site would be suitable for siting of the absorption system.

Also, one field infiltration test was performed at the retention pond location. Based on the field infiltration test conducted, the measured infiltration rate at the proposed retention pond is greater than 8 inches per minute. The appropriate factor of safety in the City and County of Honolulu Stormwater BMP Guide should be used to determine the design infiltration rate. 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. 7289-00 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 Combined Support Maintenance

Shop No. 2 project at Keaukaha Military Reservation in Hilo on the Island of 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 presents our geotechnical recommendations derived from our analyses for design of building foundations, retaining structures, site grading, pavements, sewer and stormwater disposal systems, and underground utilities only. 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 Keaukaha Military Reservation in Hilo on the Island of

Hawaii. The project involves construction of a Combined Support Maintenance Shop

(CSMS) facility that provides a surface vehicle maintenance/training facility to support the Hawaii Army National Guard. The facility will include 42,750 square feet of administration and office buildings and work shop bays. The column loads are estimated to be approximately 100 to 150 kips at the work bay area and 50 to 75 kips at the administration area. Wall loads are estimated to be approximately 3 kips per lineal foot.

Access roads and military vehicle parking and aprons are also planned for the facility. We understand that both flexible and rigid pavements will be used. In addition, a sewage disposal system consisting of a leach field and surface water runoff disposal system consisting of a retention pond are planned to service the facility. We understand that the site grading work for the project will consist of cuts and fills on the order of about 2 feet or less.

1.3 Purpose and Scope

The purpose of our exploration was to obtain an overview of the subsurface conditions at the project site to develop a generalized soil/rock data set to formulate

SECTION 1. GENERAL

W.O. 7289-00 GEOLABS, INC. Page 2 geotechnical recommendations for the design of the project. Our work was performed in general accordance with our fee proposal dated September 4, 2015. The scope of work for this exploration included the following tasks and work efforts:

1. Coordination of underground utility toning by our geologist.

2. Submittal of activity hazard analysis and safety action plan prior to commencement of field exploration.

3. Mobilization and demobilization of a bulldozer for clearing of trails at the southern portion of the site to allow access for our truck-mounted drill rig.

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

5. Drilling and sampling of 16 borings to depths of about 10 to 50 feet below the existing ground surface. In addition, 2 borings were drilled at the proposed leach field and retention pond locations. These borings each extended to a depth of about 5 feet below the existing ground surface.

6. Conduct one field percolation test in general accordance with the State of Hawaii, Department of Health's Administrative Rules, Chapter 11-62-31.2, "Wastewater Systems" and Chapter 10 of the Ten State’s Standards to evaluate the percolation characteristics of the subsurface soils for disposal of wastewater effluent.

7. Conduct one field infiltration test to evaluate the infiltration characteristics of the subsurface soils for disposal of stormwater runoff.

8. Coordinating the field exploration and logging of borings by our geologist.

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

10. Engineering analyses of the field and laboratory data to formulate geotechnical recommendations for the project design.

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

12. Coordinating our overall work on the project by our engineer.

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

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

SECTION 1. GENERAL

W.O. 7289-00 GEOLABS, INC. Page 3

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. The percolation and field infiltration test results are presented in Appendix C and Appendix D, respectively. Photographs of the core samples are presented in Appendix E.

END OF GENERAL

W.O. 7289-00 GEOLABS, INC. Page 4

SECTION 2. SITE CHARACTERIZATION

2.1 Regional Geology

The Island of Hawaii is the largest in the Hawaiian Archipelago and covers an area of approximately 4,000 square miles. The island was formed by the activity of the following five shield volcanoes: Kohala (long extinct), Mauna Kea (activity during recent geologic time), Hualalai (last erupted in 1801 to 1803), and Mauna Loa and Kilauea

(both still active).

The project site is situated on the northeastern flank of the Mauna Loa Shield

Volcano, which had been built up by the successive accumulation of basaltic lava flows and pyroclastic materials. The lava formation encountered at the site appears to consist of both a'a and pahoehoe type flows, which spread and ponded as they approached the ocean. A’a lava is typically characterized by a porous, rough, and irregular flow surface resembling a jagged accumulation of rock fragments including cobbles and boulders.

Pahoehoe is characterized by a smooth, rope-like or billowy surface and an internal structure of vesicular (porous) rock.

Cavities are commonly encountered in basaltic lavas, especially pahoehoe type lava. Cavities form when lavas are still in a molten state and they represent both lava tubes (intra-flow cavities) and blisters and pockets (inter-flow cavities). Lava tubes form when molten lava drains from the cooling flow, leaving a hollow tube-like structure, which may extend for a large longitudinal distance along the flow. Blisters and pockets are generally smaller in horizontal extent.

Basalt is considered to be a relatively permeable rock and can transmit water quite readily in both the horizontal and vertical directions. In general, water is transmitted through the porous rock matrix, along joints, fractures and inter-flow contacts, cavities, and along clinker layers. Clinker and cavities serve as primary water transmission features because of their high permeability.

2.2 Site Description

The Combined Support Maintenance Shop No. 2 project site is within the

Keaukaha Military Reservation in the District of South Hilo on the Island of Hawaii. The

SECTION 2. SITE CHARACTERIZATION

W.O. 7289-00 GEOLABS, INC. Page 5 project site is situated along the south end of Earl’s Circle. The project location is shown on the Site Plan, Plate 2.

The site is generally open land with several existing structures. Based on the topographic survey map provided, the project site is generally flat. The south side of the site is moderately vegetated. The existing ground surface elevations range from about

+66 Mean Sea Level (MSL) at the northeast side of the site to about +70 feet MSL at the southwest side of the site.

2.3 Subsurface Conditions

The subsurface conditions at the site were explored by drilling and sampling sixteen borings, designated as Boring Nos. 1 through 16, extending to depths of about

10 to 50 feet below the existing ground surface. In addition, two borings designated as

P-1 and P-2 were drilled at the proposed leach field and retention pond locations, respectively. P-1 and P-2 each extended to a depth of about 5 feet below the existing ground surface. The approximate boring locations are shown on the Site Plan, Plate 2.

In general, the site is underlain by fill of about 3 to 8 feet thick. The fill generally consisted of medium dense to dense sandy gravel. Our borings encountered some localized loose zones in the fill layer. Below the surface fill, a layer of clinker (basaltic fragments) was encountered extending to depths of about 7 to 11 feet below the existing ground surface. Basalt rock formation was encountered below the fill and clinker extending to the maximum depths explored of about 10 to 50 feet below the existing ground surface. In general, the basalt rock encountered at the site was medium hard to hard.

The subsurface conditions at the leach field and retention pond locations generally encountered dense gravelly sand and sandy gravel extending to the maximum depth explored of about 5 feet below the existing ground surface.

We did not encounter groundwater in the borings at the time of our field exploration. It should be noted that groundwater levels may vary due to surface runoffs, seasonal precipitation and other factors.

W.O. 7289-00 GEOLABS, INC. Page 6

Detailed descriptions of the field exploration methodology are presented in

Appendix A. Descriptions and graphic representations of the materials encountered in the borings are presented on the Logs of Borings in Appendix A. Laboratory tests were performed on selected soil and rock core samples and the test results are presented in

Appendix B.

2.4 Seismic Design Considerations

Based on the International Building Code (2006 Edition), the project site may be subject to seismic activity, and seismic design considerations will need to be addressed.

The following sections provide discussions on the seismicity, soil profile type for seismic design, and the potential for liquefaction at the project site.

2.4.1 Earthquake and Seismicity

Generally, earthquakes that occur throughout the world are caused by shifts in the tectonic plates. In contrast, earthquake activity in Hawaii is linked primarily 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 the 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 active volcanoes located in the southern portion of the Island of Hawaii.

The Island of Hawaii has experienced numerous earthquakes greater than

Magnitude 6 (M6+) including the October 15, 2006 earthquakes. Based on

W.O. 7289-00 GEOLABS, INC. Page 7 information obtained from the United States Geological Survey (USGS) Bulletin

2006, the following is a list of some destructive earthquakes that occurred on the

Island of Hawaii since 1868.

DATE LOCATION MAGNITUDE

March 28, 1868 South Hawaii 7.0

April 2, 1868 South Hawaii 7.9

October 5, 1929 Hualalai 6.5

August 21, 1951 Kona 6.9

April 26, 1973 North Hilo 6.2

November 29, 1975 Kalapana 7.2

November 16, 1983 Kaoiki 6.7

June 25, 1989 Kalapana 6.2

October 15, 2006 Kiholo Bay/Hawi 6.7 / 6.0

It should be noted that several of the significant earthquakes on the Island of

Hawaii have occurred on the west side in the past 100 years, including two earthquakes greater than Magnitude 6 in 1929 and 1951. In addition, the

October 15, 2006 earthquakes occurred at the northwestern portion of the island.

Therefore, it may be concluded that the west side of the Island of Hawaii could experience moderate to severe earthquakes and associated ground shaking, depending on the earthquake origin.

2.4.2 Liquefaction

Based on the anticipated subsurface conditions, the phenomenon of soil liquefaction is not a design consideration for this project site. The risk for potential liquefaction is non-existent at this project site based on the absence of groundwater at the site.

2.4.3 Soil Profile Type For Seismic Design

The subsurface conditions generally consist of fill underlain by clinker over basalt rock formation. The basalt rock was encountered at depths of about 7 to 11 feet below the existing ground surface. Based on the subsurface materials anticipated below the foundation subgrade level and the geologic setting of the area, we

W.O. 7289-00 GEOLABS, INC. Page 8 anticipate the project site may be classified from a seismic analysis standpoint as being a “Very Dense Soil and Soft Rock” site corresponding to a Site Class C soil profile based on International Building Code (Table No. 1613.5.2), 2006 Edition.

Based on Site Class C, 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) = 0.50g

Spectral Response Acceleration (Site Class B), SS = 1.50g

Spectral Response Acceleration (Site Class B), S1 = 0.60g

Site Class = “C”

Site Coefficient, Fpga = 1.00

Site Coefficient, Fa = 1.00

Site Coefficient, Fv = 1.30

Design Peak Ground Acceleration, PGA (Site Class C) = 0.33g

Design Spectral Response Acceleration, SDS = 1.00g

Design Spectral Response Acceleration, SD1 = 0.52g

Seismic Design Category = “D”

END OF SITE CHARACTERIZATION

W.O. 7289-00 GEOLABS, INC. Page 9

SECTION 3. DISCUSSION AND RECOMMENDATIONS

Based on the subsurface conditions anticipated at the project site, we recommend using shallow spread and/or continuous strip footings to support the new structures planned. As an alternative, the foundations for support of the new structures also may consist of thickened-edge slab footings.

Because cavities and/or voids are commonly present in the basaltic lava flows, we recommend implementing a program of cavity probing and grouting of the foundation locations supported on less than 5 feet of compacted fills or on-site soils.

The primary purpose of probing and grouting the foundation locations is to reduce the potential for loss of foundation support resulting from the collapse of cavities and/or the migration of fine materials into voids below the foundation. Where new building foundations are supported on more than 5 feet of compacted fills (clinker or basalt formation is at least 5 feet or deeper below bottom of footings), probing and grouting of the foundations may be omitted.

One percolation test was performed at the proposed leach field location in general accordance with the procedures outlined by the Department of Health for the design of individual wastewater systems (IWS). Based on the percolation test conducted, the percolation rate at the proposed leach field location is less than 1 minute per inch. In accordance with the "Manual of Septic-Tank Practice" prepared by the

U.S. Department of Health, Education, and Welfare, the leach field location with the percolation rate obtained at the site would be suitable for siting of the absorption system.

One field infiltration test was performed at the retention pond location. Based on the field infiltration test conducted, the measured infiltration rate at the proposed retention pond is greater than 8 inches per minute. It should be noted that the appropriate factor of safety in Table 5 of the City and County of Honolulu Stormwater

BMP Guide dated December 2012 should be used to determine the design infiltration rate.

W.O. 7289-00 GEOLABS, INC. Page 10

Detailed discussion of these items and our geotechnical recommendations for the design of foundations, retaining structures, site grading, pavements, sewer and stormwater disposal systems, and underground utilities for the project are presented in the following sections.

3.1 Building Foundations

We understand the new structures for the project generally will consist of one story buildings. Based on the subsurface conditions anticipated at the project site

(after site grading), we recommend utilizing shallow spread and/or continuous strip footings to support the new structures planned. As an alternative, foundations for support of the new structures also may consist of thickened-edge slab footings.

Our borings encountered a surface layer of sandy gravel fill ranging from about

3 to 8 feet in thickness. Some loose soil pockets were encountered in the fill layer.

Therefore, loose materials encountered at the foundation subgrades should be over-excavated to expose the underlying firm materials. The over-excavation may be backfilled with the on-site granular soils or structural fill material, placed in level lifts not exceeding 8 inches in loose thickness, moisture-conditioned to above the optimum moisture content, and compacted to at least 95 percent relative compaction. As an alternative to backfilling with compacted fill, the foundations may be extended to bear on the underlying competent materials.

An allowable bearing pressure of up to 3,500 pounds per square foot (psf) may be used for the design of footings bearing on compacted structural fill or on-site compacted granular materials. 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.

In general, the bottom of footings should be embedded a minimum of 18 inches below the lowest adjacent finished grade. Footings constructed near the tops of slopes or on slopes should be embedded deep enough such that the horizontal distance measured from the outside edge (at the base of the footing) to the face of the slope is no less than 6 feet.

W.O. 7289-00 GEOLABS, INC. Page 11

In addition, foundations next to other foundations, utility trenches, easements or other retaining walls should be embedded below a 45-degree imaginary plane extending upward from the bottom edge of the structure or utility trench, or the footings should extend to a depth as deep as the inverts of the utility lines. This requirement is necessary to avoid surcharging adjacent below-grade structures with additional structural loads and to reduce the potential for appreciable foundation settlement.

If the foundations are designed and constructed in strict accordance with our recommendations, we estimate the total settlements of the foundations to be less than

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

Lateral loads acting on the structures may be resisted by friction between the bottom of the foundation and the bearing materials and by passive earth pressure acting against the near-vertical faces of the foundation system. A coefficient of friction of 0.45 may be used for footings bearing on the compacted fill materials, re-compacted on-site materials, or basalt formation. Resistance due to passive earth pressure may be estimated using an equivalent fluid pressure of 450 pounds per square foot per foot of depth (pcf) (Kp = 3.5) assuming the soils around the footings are well compacted for a level ground surface condition. The passive pressure resistance in the upper 12 inches of the soil should be neglected unless covered by pavements or slabs.

A Geolabs representative should observe the footing excavations prior to the placement of reinforcing steel and concrete to confirm the foundation bearing conditions and the required embedment depths.

3.2 Probing and Grouting

Based on our experience in the vicinity, cavities and/or voids are commonly encountered in the basaltic lava flows at the project site. To reduce the potential for loss of foundation support resulting from the collapse of cavities and/or the migration of fine materials into voids below the foundations, we recommend implementing a program of cavity probing and grouting of the foundation locations supported on 5 feet or less of compacted fills or on-site soils. Where new building foundations are supported on more

W.O. 7289-00 GEOLABS, INC. Page 12 than 5 feet of compacted fills or on-site soils (clinker and basalt formation is at least

5 feet or deeper below bottom of footings), probing and grouting of the foundations may be omitted. In addition, the probing and grouting program may be omitted for non-bearing walls, such as partition walls and site retaining walls.

For estimating purposes, we recommend drilling probe holes, where required, at

10-foot on centers for the thickened-edge slab footings (or other continuous strip footings) of the new structures. In addition, at least one probe hole should be drilled for every 50 square feet of isolated spread footing location. The probe holes should be at least 3 inches in diameter and should extend to at least 10 feet below the planned bottom of foundation elevation. If cavities and/or voids are encountered or suspected during the probing operation, additional probe holes should be drilled at closer spacing to help delineate the vertical and lateral extent of the cavity and/or void.

The probe holes and cavities discovered should be backfilled with controlled low strength material (CLSM) with a slump of about 6 to 9 inches. The CLSM should be injected at low to moderate pressures. As an alternate to CLSM, sand-cement grout with a slump of about 6 to 9 inches also may be used.

Because of the potential for encountering cavities and/or voids at the project site, we recommend obtaining unit prices for additional probing and grouting during bidding or pricing of the work. In addition, the probe drill should be available on-site until the probing and grouting operations are completed. The contractor also should be aware that a longer lag time between probing/grouting operations and foundation construction might be required in the construction schedule.

A Geolabs representative should monitor the probing and grouting operations to observe the presence of cavities and/or voids in the subsurface and to allow for additional recommendations to be made if excess grout take and/or changed conditions are observed. Observation of the probing and grouting operations for the building foundations should be designated as a “Special Inspection” item.

W.O. 7289-00 GEOLABS, INC. Page 13

3.3 Slabs-On-Grade

We anticipate concrete slabs-on-grade will be used for the ground floors of the new structures. For the interior building slabs (not subjected to vehicular traffic), we recommend providing a minimum 4-inch thick layer of cushion fill below the slabs for uniform support. The cushion fill should consist of open-graded gravel (ASTM C33, No. 67 gradation) and also would serve as a capillary moisture break. To reduce the potential for excessive moisture infiltration and subsequent damage to floor coverings, an impervious moisture barrier is recommended on top of the gravel cushion fill layer.

Flexible floor coverings should be considered above the floor slab because they can better mask minor slab cracking.

Where slabs are subjected to vehicular traffic or sustained vibrations, a minimum of 6 inches of compacted aggregate subbase course (3-inch minus granular materials) should be provided below the slabs in lieu of the 4-inch thick cushion fill layer. The moisture barrier may be omitted for these slabs. The aggregate subbase course layer should be moisture-conditioned to above the optimum moisture content and compacted to a minimum of 95 percent relative compaction. For the design of structural slabs, a modulus of subgrade reaction of about 300 pounds per square inch per inch of deflection (pci) may be used for design of the slabs.

In addition, we envision that exterior concrete walkways and exterior flatwork likely will be required for the project. In general, we recommend providing a minimum

4-inch thick cushion fill layer of open-graded gravel (ASTM C33, No. 67 gradation) or aggregate subbase below exterior concrete slabs that will not be subjected to vehicular traffic. The aggregate subbase should be compacted to at least 90 percent relative compaction. To reduce the potential for substantial shrinkage cracks in the concrete slabs, crack control joints should be provided at intervals equal to the width of the walkways (or slabs) with expansion joints at right-angle intersections.

3.4 Retaining Structures

The following general guidelines are provided and may be used for design of retaining structures at the project site.

W.O. 7289-00 GEOLABS, INC. Page 14

3.4.1 Retaining Structure Foundations

In general, we believe the retaining structure foundations may be designed in accordance with the recommendations and parameters presented in the

"Building Foundations" section herein. However, the retaining structure footings should have a minimum width of 18 inches. In addition, the bottom of wall foundations on relatively flat areas should be embedded a minimum depth of

24 inches below the lowest adjacent finished grade.

3.4.2 Static Lateral Earth Pressures

In general, retaining structures should be designed to resist the lateral earth pressures due to the adjacent soils and surcharge effects. The recommended lateral earth pressures for design of retaining structures, expressed in equivalent fluid pressures of pounds per square foot per foot of depth (pcf), are presented in the following table.

LATERAL EARTH PRESSURES

FOR DESIGN OF RETAINING STRUCTURES

Backfill Condition

Active (pcf)

At-Rest

(pcf)

Level Backfill

(Ka = 0.24)

(Ko = 0.38)

The lateral earth pressures shown above do not include hydrostatic pressures that might be caused by groundwater trapped behind the structures. The values provided above assume that granular soils less than 3 inches in maximum dimension will be used to backfill directly behind the retaining structures. The zone of granular soils with a maximum particle size of 3 inches should extend a minimum of 3 feet laterally behind the retaining walls. Backfill beyond this 3-foot zone may consist of structural fills consisting of well-graded granular materials less than 6 inches in largest dimension.

It is assumed that the backfill behind retaining structures will be compacted to between 90 and 95 percent relative compaction. Over-compaction of the

W.O. 7289-00 GEOLABS, INC. Page 15 retaining structure backfill should be avoided. In general, an active condition may be used for gravity retaining walls and retaining structures that are free to deflect laterally by as much as 0.5 percent of the structure height. If the tops of the structures are not free to deflect beyond this degree, or are restrained, the retaining structures should be designed for the at-rest condition.

Surcharge stresses due to areal surcharges, line loads, and point loads within a horizontal distance equal to the depth of the retaining structure should be considered in the design. For uniform surcharge stresses imposed on the loaded side of the structure, a rectangular distribution with uniform pressure equal to

24 percent of the vertical surcharge pressure acting on the entire height of the structure, which is free to deflect (cantilever), may be used in design. For retaining structures that are restrained, a rectangular distribution equal to

38 percent of the vertical surcharge pressure acting over the entire height of the structure may be used for design. Additional analyses during design may be needed to evaluate the surcharge effects of point loads and line loads.

3.4.3 Dynamic Lateral Earth Forces

Dynamic lateral earth forces due to seismic loading will need to be considered in the design of the retaining structures. Seismic loading (Design PGA = 0.33g) is used to estimate the dynamic lateral earth pressures. The table below summarizes the dynamic lateral earth forces acting on the retaining structure in the event of an earthquake versus the estimated wall displacements.

DYNAMIC LATERAL EARTH FORCES

FOR RETAINING STRUCTURES

Lateral Movement (inches)

Dynamic Lateral Earth Forces (H2 pounds per linear foot)

Level Backfill

1 20.0

2 13.5

3 8.2

W.O. 7289-00 GEOLABS, INC. Page 16

Please note that the above table only applies to a level backfill condition, where H is the height of the structure in feet. The resultant force should be assumed to act through the mid-height of the structure. The above dynamic lateral earth forces are in addition to the static lateral earth pressures provided previously. An appropriately reduced factor of safety may be used when dynamic lateral earth pressures are accounted for in the design of the retaining structure.

3.4.4 Drainage

In general, retaining structures should be well drained to reduce the potential for build-up of hydrostatic pressures. A typical drainage system would consist of a

12-inch wide zone of permeable material, such as open-graded gravel

(ASTM C 33, No. 67 gradation), placed directly around a perforated pipe

(perforations down) at the base of the retaining structure. The perforated pipe should discharge to an appropriate outlet or weepholes.

As an alternative, a prefabricated drainage product, such as MiraDrain or

EnkaDrain, may be used instead of the permeable drainage material. The prefabricated drainage product also should be hydraulically connected to a perforated pipe at the base of the retaining structure. Unless covered by concrete or asphaltic concrete, the upper 12 inches of backfill should consist of relatively impervious materials, such as well-graded soils, to reduce the potential for significant water infiltration behind the retaining structures.

3.5 Site Grading

We understand that site grading for the project will generally consist of cuts and fills of about 2 feet or less. Deeper excavations may be required for the construction of the retention pond. 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

5. Cut and Fill Slopes

W.O. 7289-00 GEOLABS, INC. Page 17

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.

3.5.1 Site Preparation

At the on-set of earthwork, areas within the contract grading limits should be cleared and grubbed thoroughly. Vegetation, debris, deleterious materials, and other unsuitable materials should be removed and disposed properly off-site to reduce the potential for contamination of the excavated materials to be used as fill materials.

Foundations and slabs of the existing structures 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. The on-site materials should be moisture-conditioned to above the optimum moisture content, placed in

6 to 8-inch level loose lifts, and compacted to a minimum of 90 percent relative compaction. Utilities to be abandoned in-place under the proposed structure should be backfilled by pumping lean concrete or CLSM (Controlled Low Strength

Material) under low pressure.

Finished subgrades in cut areas and areas to be filled should be proof-rolled with a minimum 15-ton (static weight) vibratory drum roller for a minimum of eight passes to help detect and collapse near-surface cavities and/or voids. The vibratory drum roller also should be operated at a speed of about 300 feet per minute. A Geolabs representative should observe the proof-rolling operations. Yielding areas, loose areas, or cavities disclosed during clearing and proof-rolling operations should be over-excavated and backfilled with compacted fill materials. Additive and deductive unit prices should be obtained for over-excavation of the collapsed lava tube features (and other features) and backfilled with compacted fill to account for variations in the over-excavation and backfill quantities.

W.O. 7289-00 GEOLABS, INC. Page 18

3.5.2 Fills and Backfills

In general, structural fill should be used at the site. Structural fill materials should consist of well-graded granular materials generally less than 6 inches in maximum dimension with sufficient fines to prevent the occurrence of voids in the compacted mass. In addition, structural fill materials should contain less than 30 percent particles passing the No. 200 sieve by weight. In general, the excavated on-site materials may be reused as a source of structural fill materials, provided that they are processed to meet the maximum particle size and gradation requirements presented above.

Imported fill materials, if required, should be free of organics and deleterious materials and should be suitable for the intended use based on the recommendations for fill materials provided herein. In addition, a Geolabs representative should observe and/or test imported materials prior to being transported to the project site for the intended use.

3.5.3 Fill Placement and Compaction Requirements

Structural fill materials should be placed in level lifts not exceeding 12 inches in loose thickness, moisture-conditioned to above the optimum moisture content, and compacted to at least 95 percent relative compaction. Relative compaction refers to the in-place dry density of soil expressed as a percentage of the maximum dry density of the same soil established in accordance with ASTM D1557. Optimum moisture is the water content (percentage by weight) corresponding to the maximum dry density. Compaction should be accomplished by sheepsfoot rollers, vibratory rollers, or other types of acceptable compaction equipment.

Conventional compaction testing is generally not practical in fills composed of rocks, boulders, and/or cobbles. Instead, a testing program should be conducted at the start of the grading phase of the project under the observation of a Geolabs representative to evaluate the number of passes needed to achieve the desired level of compaction. Based on this testing program, the number of passes may then be used as the field criterion for adequate compaction.

W.O. 7289-00 GEOLABS, INC. Page 19

For preliminary estimating purposes, compaction may be accomplished by using a large vibratory drum roller having a static weight of at least 15 tons traveling at a speed of about 300 feet per minute. The roller should pass over the fill surface at least eight times for structural fill.

3.5.4 Excavation

Based on our field exploration, the project site is underlain by silty and sandy gravel soils overlying clinker and basalt formation. It is anticipated that the surface soils, clinker, and severely to closely fractured basalt formation may be excavated readily with normal heavy excavation equipment, such as excavators, and ripped with large bulldozers. However, some of the deeper excavations into the moderately fractured, medium hard to hard basalt may require the use of hoerams or chipping.

The above discussions regarding the rippability of the surface materials are based on our visual observation of the existing basalt formation and field data from the borings. Contractors should be encouraged to examine the site conditions and the subsurface data to make their own reasonable and prudent interpretation.

Based on Section V: Chapter 2 of the Occupational Safety and Health

Administration (OSHA) Technical Manual, the soils encountered at the project site may be classified as follows:

Soil Description Soil Type

Sandy Gravel (Fill) and Clinker Type B

Basalt Rock Stable Rock

The soil types presented in the above table may be used to determine the temporary maximum allowable slope inclinations for excavation sidewalls.

3.5.5 Cut and Fill Slopes

In general, cut slopes and permanent fill slopes may be designed with a slope inclination of 2H:1V or flatter. This assumes that the fill slopes will be constructed

W.O. 7289-00 GEOLABS, INC. Page 20 using structural fills. In addition, fills placed on slopes steeper than 5H:1V should be keyed and benched.

In general, the filling operations should start at the lowest point and continue up in level horizontal compacted layers in accordance with the above fill placement recommendations. Fill slopes should be constructed by overfilling and cutting back to the design slope ratio to obtain a well-compacted slope face. The fill slope face should be finished to a relatively smooth and well-compacted surface. In addition, surface water should be diverted away from the tops of slopes, and slope planting should be provided as soon as possible to reduce the potential for significant erosion of the finished slopes.

3.6 Pavements

We understand that access roads, hard stands, and parking areas are planned for the project. We anticipate that the new pavements will bear on both new structural fill and the granular on-site soils. Assuming that the pavement subgrade soils will consist of the recompacted on-site soils encountered during our exploration and/or structural fill, we recommend using the following design soil parameters for use in the pavement design.

SOIL PARAMETERS FOR PAVEMENT DESIGN

Pavement Subgrade Soils CBR k (psi/in)

MR

(psi)

(degrees) c’

(psf)

Structural Fill/Granular On- Site Soils

30 300 22,500 38 0

The above soil parameters are applicable provided that the pavement subgrade preparation mentioned below is conducted during pavement construction. The subgrade soils under the pavement areas should be scarified to a depth of about 12 inches, moisture-conditioned to above the optimum moisture content, and compacted to a minimum of 95 percent relative compaction. Soft and/or loose soils encountered at the pavement subgrade should be over-excavated to the underlying firm or dense materials.

The resulting over-excavation should be backfilled with compacted structural fill.

W.O. 7289-00 GEOLABS, INC. Page 21

Paved areas should be sloped, and drainage gradients should be maintained to carry surface water off-site. Surface water ponding should not be allowed on the site during or after construction. A subdrain system is recommended to collect the excess water from landscaping irrigation.

3.7 Utility Lines

We envision new underground utility lines will be required for the project development. We anticipate most of the trenches for the utility lines will be excavated in the granular fill, clinker, or basalt rock encountered in our…