W912HV-16-B-0002_Appendix_C_Geotechnical_Investigation_Report.pdf

In Conjunction With:

Geotechnical Investigation Report (FINAL)

FY15 DoDEA MILCON Project, PA00017 Replace E.C. Killin Elementary School

Camp Foster, Okinawa, Japan

US Army Corps of Engineers, Japan Engineer District Contract No. W911HV-11-D-0004

ESC Project No. 1454

14 March 2014

Prepared For:

Jacobs Government Services Company 4300 B Street, Suite 600

Anchorage, AK 99503 T 907 563 3322 F 907 563 3320

Prepared By:

THIS PAGE IS INTENTIONALLY BLANK

Geotechnical Investigation Report i

EXECUTIVE SUMMARY

A geotechnical investigation was conducted at the existing E.C. Killin Elementary School (KES) site in Camp Foster, Okinawa, Japan in order to provide geotechnical recommendations in support of the design effort for the new KES contracted under United States Army Corps of Engineers (USACE), Japan Engineer District (JED) Contract No. W911HV-11-D-0004 to Jacobs Government Services Company (Jacobs).

The geotechnical investigation included 14 borings conducted within the existing KES facility area. All borings were advanced to variable depths to confirm the depth of the bedrock at the site. In total, approximately 150 meters of soil boring were conducted along with disturbed and undisturbed soil sampling of representative soil layers to be analyzed at a local soils laboratory for basic engineering characteristics.

Investigative drilling and soils analysis were performed in accordance to relevant Japan Industrial Standards (JIS) and the Japan Geotechnical Standard (JGS) by Shindo Soil Investigation Co., a certified soils laboratory in Okinawa Prefecture.

Non-core soil borings were performed using a 66-millimeter (mm) diameter single core tube bit and split spoon sampler with standard penetration tests (SPT) performed once per meter (m) of boring depth below ground surface (bgs). Representative soil samples were taken at key stratum and tested for soil parameters as described in Section 6.2 of this report. Soil boring logs and laboratory data are included in the report appendices.

Geologic Site Hazards and Site Class

Screening for geological site hazards to include susceptibility to liquefaction, slope failure, settlement and corrosive environments was conducted for the existing KES Site.

Subsurface conditions indicate that the potential for liquefaction is low.

Slope failure was observed at the south portion of the site between the playground and baseball field, where vegetated 2:1 (H:V) slopes were constructed to accommodate the grading of the current KES site. It is suspected that the failure occurred due to groundwater variations after rainfall events. New retaining walls proposed in this area will contribute to stabilizing these slopes.

Settlement and consequent lateral ground movement were observed at the north portion of the site, at the boundary fence of the Camp Foster installation. This area is adjoining a steep slope that does not present signs of failure. However, settlement and lateral ground movement are affecting nearby structures. For instance, along the fence line, fence posts and light poles are tilting, and cracks and subsidence in concrete sidewalks can be observed. Similarly, an existing concrete block retaining wall shows displacements on the order of 50 to 100 mm.

Geotechnical Investigation Report ii

The foundations for the new KES are adequately isolated from the slope and supported by improved soils. Therefore, settlement or lateral ground movement that may affect the building foundation is likely to be negligible. However, ground reinforcement needs to be considered for the new fire lane road planned in this area.

Environmental soil test results indicate that surface cohesive fill and mudstone soils may be corrosive. Clayey soils may be considered mildly corrosive according to the US National Association of Corrosion Engineers (NACE) guidelines.

Field investigation and laboratory test results indicate that the site soils fit the Site Class “D” designation for seismic considerations. The hard mudstone bedrock which presented SPT N-values greater than 50 and was encountered within the top 30 m of soils were factors in selecting a Site Class “D” designation for the KES site.

Details on geological site hazards and site class determination are described in Sections 5.2 and

5.3 of this report.

KES Subsurface Conditions

Site soils consist mainly of surface fill layers of cohesive soils overlying soft to medium stiff clays followed by mudstone soils. The mudstone layer is considered the bedrock of the site.

Fill soils at the site are typically composed of a mixture of clay and mudstone soils occasionally interspersed with gravel particles and construction debris such as crushed concrete pieces and medium to large size rock chunks. There are no records available for the placement of this fill since it was probably dumped during past construction activities at the site. Thickness of this undocumented and uncontrolled fill vary throughout the site. For instance, at the central portion of the site, in between the existing playground area and the baseball field, the thickness of fill soil layers range from 2 to 6 m. Based on the distribution of the fill layers and the presence of soft alluvial clays, it is assumed that a former ravine was located crossing the central area of the proposed new KES, from south to north. The thickness of fill soil layers at the existing parking lot and the easternmost and southernmost areas of the site are relatively thin, ranging from 0.5 to 1 m. Underlying the fill soils, natural soft to medium stiff clay soils with high plasticity and mudstone bedrock layers with stiff to hard consistencies were observed.

The mudstone bedrock layer is considered a candidate bearing layer to support the foundations of the new KES structures.

Groundwater was observed in some of the borings. During rainy seasons, groundwater likely perches within the existing fill, above the top of the mudstone bedrock. The natural groundwater elevation is considered to be approximately 26 m above mean sea level (MSL) which coincides in elevation with the middle portion of the vegetated slopes located at the south area of the site.

Geotechnical Investigation Report iii

KES Site Grading Considerations

According to correspondence with Jacobs team designers, the proposed KES site elevation will be similar to the existing elevation of the baseball field. In addition, based on the footprint of the new KES, cut and fill operations will be required during the grading of the site. Approximate 1 and 2 m of fill may be required at the existing playground and parking lot areas, respectively.

Extensive cut operations are expected at the south portion of the site where existing vegetated 2:1 (H:V) slopes are located. Cut is expected to be mostly in clay and mudstone soils. Although mudstone soils present hard consistency, they can be excavated using conventional heavy equipment. During cut operations, the presence of groundwater can be expected. Construction of new retaining walls as a result of cut operations are planned in this area. Expected heights of new retaining walls are 8 m maximum and 5 m on average. Recommendations for retaining walls and values for earth pressures acting against the retaining walls are presented in Section 7.2 of this report.

KES Structure Foundation and Floor Slab Considerations

Based on our investigations, in order to implement a shallow foundation system for the new KES facilities, soil improvement is required at areas where soft/medium stiff clays and thick layers of undocumented fills are encountered at the site. In order to provide adequate support, soil improvement should be extended to a depth where mudstone bedrock layers are located.

Shallow and deep soil mixing systems consisting of soil-cement slurry and soil-cement columns, respectively, are recommended as soil improvement methods for this project. For locations where the mudstone bedrock bearing layer is located within 4 m of the new finished grade, soil improvement by means of soil-cement slurry is recommended. Soil-cement columns are recommended for locations where the mudstone bedrock bearing layer is located at depths greater than 4 m below finish grade.

Recommended allowable bearing pressures for shallow foundations with soil improvement are recommended to be 300 KN/m2. An increment of 1/3 of this allowable bearing pressure can be considered for short-term loads such as earthquake and short-time wind loads. In order to achieve the recommended bearing pressures, soil improvement must extend to depths where mudstone layers with SPT N-values greater than 30 are encountered. For cost estimating purposes, an average soil-cement column length of approximately 7 meters may be assumed, considering a minimum depth of penetration for footings of 1 m below finished grade. In addition, soil-cement columns are expected to be between 800 and 1,200 mm in diameter.

Minimum design compressive strength for soil-cement columns and soil-cement slurry should be 1,400 KN/m2 and 1,000 KN/m2, respectively.

The estimated total settlement of shallow foundations with soil improvement resting in mudstone layers based on the above conditions, and using columns loads provided by Jacobs, is calculated to be less than 25 mm. Estimated differential settlement is calculated to be less than 10mm.

Graphical representations of the target bearing layer are shown in soil boring logs and soil profiles included in Appendix A and B, respectively.

Geotechnical Investigation Report iv

The uncertainty of fill soils quality and engineering behavior, inconsistency of material distribution and grade of compaction, and variation in thickness of the undocumented fill covering the central portion of the proposed new KES may lead to excessive differential settlement, which can affect the performance of a conventional slab-on-grade. For example, the north portion of the site, where settlement is affecting structures along the fence line, is comprised of fill soils. Furthermore, since this area has not been designated to support main structures (this portion of the site is currently occupied by the playground and baseball field), it is suspected that proper care was not taken when selecting and placing fill soil materials. This undocumented fill underlies more than half of the footprint of the proposed new KES and has a depth of 4 meters on average. Based on these conditions, complete removal of this undocumented fill layer and consequent replacement with satisfactory materials is considered very costly. Therefore, a structural slab is recommended for the KES facilities.

Pavement Recommendations

As part of the geotechnical investigation, seven soil samples for CBR tests were extracted at locations where new pavements are proposed at the site, for development of flexible and rigid pavement design recommendations. Based on the results of CBR testing the following pavement sections are recommended based UFC 3-240-01FA, "Pavement Design for Roads, Streets, Walks and Open Storage Areas", dated on 16 January 2004.

SUMMARY FOR FLEXIBLE PAVEMENT RECOMMENDATIONS

Site Area

Bituminous Pavement Thickness

(mm)

Base Course Thickness

(mm)

Subbase Thickness

(mm)

Total Pavement Thickness

(mm) Staff and Visitor Parking Lot Area (Area A)

50 150 200 400

Staff and Visitor Parking Lot Area (Area B)

50 150 300 500

Bus Drop-Off Area 75 150 350 575

Fire Lane Road 75 150 275 500

SUMMARY FOR RIGID PAVEMENT RECOMMENDATIONS

Site Area PCC layer Thickness

(mm)

Base Course Thickness

(mm)

Total Pavement Thickness

(mm) Service road close to the service entry canopy

150 150 300

Details for flexible and rigid pavement recommendations are presented in Section 7.3 of this report.

Geotechnical Investigation Report v

CONTENTS

EXECUTIVE SUMMARY ................................................................................................................... i

ACRONYMS AND ABBREVIATIONS ........................................................................................... vii

1.0 INTRODUCTION

2.0 SITE OVERVIEW

3.0 SITE GEOGRAPHICAL AND GEOLOGICAL FEATURES

4.0 PROJECT CONSIDERATIONS

5.0 SITE CONDITIONS

5.1 Subsurface Conditions

5.1.1 Subsurface Profile of the Site

5.1.2 Groundwater

5.1.3 Subsurface Variations

5.2 Geological Site Hazards

5.2.1 Soil Liquefaction

5.2.2 Potential Slope Failures and Settlement

5.2.3 Corrosive Soil Environments

5.3 Site Class Designation

6.0 FIELD EFFORT

6.1 Soil Borings and Standard Penetration Testing

6.2 Soils Laboratory Testing

7.0 CONCLUSIONS & RECOMMENDATIONS

7.1 Foundation and Floor Slab Recommendations

7.1.1 KES Main Building

7.1.2 KES Auxiliary Facilities and Other Structures

7.2 Retaining Wall Recommendations

7.3 Flexible and Rigid Pavement Recommendations

8.0 CONSTRUCTION CONSIDERATIONS

8.1 Earthwork and Grading

8.2 Site Drainage

8.3 Excavation and Trenching

8.4 Construction Considerations For Pavements

8.5 Soil Improvements

9.0 REFERENCES

Geotechnical Investigation Report vi

TABLES

TABLE 1: WATER SOLUBLE CONSTITUENTS & SOIL CONDUCTIVITY

TABLE 2: CORROSIVITY RATINGS ACCORDING TO NACE GUIDELINES

TABLE 3: SOIL BORINGS SUMMARY

TABLE 4: SOIL LABORATORY TESTING SUMMARY

TABLE 5: SOIL PARAMETERS FOR RETAINING WALLS (LEVEL BACKFILL)

TABLE 6: SOIL PARAMETERS FOR RETAINING WALLS (SLOPED BACKFILL 2:1, H:V)

TABLE 7: FLEXIBLE PAVEMENT DESIGN RECOMMENDATIONS PARAMETERS

TABLE 8: RIGID PAVEMENT DESIGN RECOMMENDATIONS PARAMETERS

TABLE 9: COMPACTION REQUIREMENTS

TABLE 10: LIFT THICKNESS REQUIREMENTS FOR BACKFILL COMPACTION

FIGURES

FIGURE 1: NEW E.C. KILLIN ELEMENTARY SCHOOL - PROPOSED SITE LOCATION MAP

FIGURE 2: SOIL BORING & CBR LOCATIONS ON CURRENT SITE LAYOUT

FIGURE 3: SOIL BORING & CBR LOCATIONS ON FUTURE SITE LAYOUT

FIGURE 4: CENTRAL OKINAWA REGION GEOLOGICAL SURFACE MAP

FIGURE 5: APPROXIMATE AREAS OF UNDOCUMENTED FILL AND SOIL IMPROVEMENT–

KES MAIN BUILDING

FIGURE 6: JIS DESIGNATED ENGINEERED BASE & SUBBASE MATERIALS FOR

PAVEMENTS

FIGURE 7: AREAS FOR PAVEMENT RECOMMENDATIONS

APPENDICES

A SOIL BORING LOGS

B SOIL PROFILES

C GEOTECHNICAL LABORATORY REPORTS

D FIELD WORK PHOTOGRAPHS

E CATALOGS FOR SOIL IMPROVEMENT INSTALLATION

Geotechnical Investigation Report vii

ACRONYMS AND ABBREVIATIONS

ASL Above sea level ASTM American Society for Testing and Materials AC Asphalt concrete B Minimum width of foundation bgs Below ground surface Bldg Building CBR California Bearing Ratio cm Centimeter DoDEA Department of Defense Education Activity ESC Environmental Science Corporation FY Fiscal Year H:V Horizontal : Vertical IBC International Building Code JED Japan Engineer District JGS Japan Geotechnical Society JIS Japan Industrial Standards JLIT Japan Ministry of Land, Infrastructure, Transport and Tourism JRA Japan Road Association KES E.C. Killin Elementary School km Kilometer km2 Square kilometer KN Kilo Newton KN/m2 Kilo Newton per square meter KPa Kilopascals m Meter m2 Square meter MILCON Military Construction mm Millimeter MPa Mega pascal MN/m3 Mega Newton per cubic meter MSL Mean sea level N Blow count of the Standard Penetration Test NACE National Association of Corrosion Engineers OSHA Occupational Safety & Health Administration PCC Portland cement concrete SOW Scope of Work SPT Standard Penetration Test UFC Unified Facilities Criteria UFGS Unified Facilities Guide Specifications US United States USACE United States Army Corps of Engineers

Geotechnical Investigation Report 1

1.0 INTRODUCTION

Environmental Science Corporation (ESC) was tasked under Jacobs Government Services Company (Jacobs) to conduct a geotechnical investigation for the FY15 DoDEA MILCON Project, PA00017 Replace E.C. Killin Elementary School (KES) located at Camp Foster, Okinawa, Japan.

The purpose of the geotechnical investigation is to provide geotechnical recommendations in support of the design effort for the new KES contracted to Jacobs under United States Army Corps of Engineers (USACE), Japan Engineer District (JED) Contract No. W911HV-11-D-0004.

The following report addresses the results of investigative soil boring and geotechnical laboratory analysis performed at the proposed KES site in Camp Foster, Okinawa, Japan.

The following describes the major work tasks associated with the contracted geotechnical investigation at the Site:

• Performed exploratory boring and soils investigation within the project site in two stages:

the first stage from 04 to 27 September 2014 and the second stage from 15 to 19 November 2014.

• Completed 14 non-core soil borings to depths which confirmed depth to the competent bearing layer for foundations and bedrock of the site. Standard penetration tests (SPT) were conducted per each meter drilled.

• Soil samples were taken at characteristic soil layers at representative boring locations. In total 8 disturbed soil samples and 7 undisturbed soil samples were taken and analyzed for physical and engineering soil properties. All samples were taken under the supervision of the project geotechnical engineer. Soil samples were tested for the following characteristics:

Density of Soil Solid particles (JIS A 1202)

Soil Moisture Content (JIS A 1203)

Soil Particle Size Distribution (JIS A 1204, JIS A 1223)

Atterberg Limits (JIS A 1205)

Consolidation Test (JIS A 1217, JGS 0411)

Unconfined Compression Test (JIS A 1216, JGS 0511)

Electric Conductivity of Soils (JGS 0212) pH (JGS 0211)

Geotechnical Investigation Report 2

Hydrosulfates and Total Chloride Content (JGS 0241)

• In addition, soil samples within the project site were collected and the following geotechnical tests were conducted:

California Bearing Ratio (CBR) (JIS A 1211, JGS 0721) (7 samples)

• Engineering analysis of the field exploration and results of laboratory testing data.

• Provided recommendations for allowable bearing pressures based on the existing soil characteristics and conditions as determined from the soil borings and laboratory testing in support of the foundation design for the new KES structures. Other recommendations for floor slabs and retaining walls are also provided.

• Review of as-built drawings and other pertinent data for the existing buildings of KES.

• Provided pavement design recommendations based on California Bearing Ratio (CBR) sampling and analysis results from 7 CBR samples taken at the site, in planned future paved areas.

• Provided construction considerations pertinent to earthwork, site grading and site drainage.

Soil boring logs, soil profiles, soil laboratory testing reports, field and laboratory photographs are included in report appendices.

Geotechnical Investigation Report 3

2.0 SITE OVERVIEW

The project site for the new KES is located in Camp Foster, Okinawa, Japan. The project site is located adjacent to a secondary road, with Prefectural Road No. 130 to the west, bounded by Zukeran District to the east, local farm lands and the Hijagawa river to the north and high-rise military housing to the south. The existing KES site is located on a flat terrace area surrounding by slopes constructed to accommodate the grading of the site. The existing KES site covers a total area of approximately 45,000 square meters (m2) of land.

Figure 1: New E.C. Killin Elementary School - Proposed Site Location Map

Soil borings were conducted on 14 locations and CBR sampling at 7 locations throughout the existing KES. Figures 2 and 3 show soil boring and CBR locations in relation to current site conditions and to future planned structures, respectively.

Geotechnical Investigation Report 4

Figure 2: Soil Boring & CBR Locations on Current Site Layout

Geotechnical Investigation Report 5

Figure 3: Soil Boring & CBR Locations on Future Site Layout

Geotechnical Investigation Report 6

3.0 SITE GEOGRAPHICAL AND GEOLOGICAL FEATURES

Okinawa is the largest island of the Ryukyus, a chain of hundreds of islands which lie in the subtropics just north of the Tropic of Cancer. The Ryukyus extend southwest in a span over 1,000 km long from Kyushu, the southernmost of Japan’s four main islands, to Taiwan. Okinawa island is located at 26°22’0” North 127°45’0” east and is approximately 103 kilometers (km) long, has an average width of 11.3 km , and covers an area of 1,176 square kilometers (km2).

The topography of the Ryukyus is characterized either by high islands consisting of uplifted ancient metamorphic, volcanic, or limestone rocks; or low lying islands consisting of limestone terrace platforms and more recent low lying coral beds. Karst topography shapes many of the features of the Ryukyus including caves, sinkholes, and plateaus.

The Okinawa main island can be divided into two distinct zones on the basis of geography and geology. The boundary between the geological zones is near the south end of a narrow isthmus within Uruma City. The northern geological zone, comprising about two-thirds of the islands, is a mountainous area with high relief and deep dissection. Scattered small villages, farms, and narrow roads are largely confined to coastal areas surrounding the central mountainous zone. The southern geological zone, consisting of approximately one-third of the island, is a less elevated and hilly country with moderate relief and only local deep dissection.

The southern geological zone of Okinawa, in which the project site is located has a variety of terrain, but is essentially an eroded upland that is lower and less rugged than the northern part of the island.

The project site is located at Camp Foster, which is situated at the south-central part of Okinawa along the East China Sea Coast as shown in the site location map, Figure 1.

Camp Foster consists of a saddle shaped region with gently sloped hilly terrain. Generally, the hilly terrain of Camp Foster is underlain by a thick layer of sedimentary limestone coral. Underneath the limestone deposits, the Shimajiri Mudstone group forms the bedrock of the central to southern region of Okinawa. The Shimajiri Mudstone bedrock was confirmed in all the soil borings, however thin limestone deposits were observed only at one soil boring conducted at the highest area of the site, close to the high-rise housing buildings. Shimajiri Mudstone is composed predominantly of bluish gray colored silty clay with lesser amounts of inter-bedded silty sand and vitreous ash.

Geological surface formations for the central portion of Okinawa island are shown in Figure 4.

Generally, the Shimajiri Mudstone formation is considerably solidified and the normal SPT N-values are in the range of 30 to over 50. Almost all structures in the southern region of Okinawa receive foundation support from this stratum.

The project site of the existing KES is relatively flat and it is located at a terrace area at an average elevation of 22 m above mean sea level (MSL). The KES site is surrounding by vegetated 2:1 (H:V) slopes and retaining walls constructed to accommodate the grading of the existing KES.

Geotechnical Investigation Report 7

Figure 4: Central Okinawa Region Geological Surface Map

Project Site

Geotechnical Investigation Report 8

4.0 PROJECT CONSIDERATIONS

The proposed new KES, which covers an approximate area of 45,000 m2, will be constructed at the existing KES site at Camp Foster, Okinawa, Japan. The new KES will be constructed after the demolition of the existing KES structures.

The main KES building facilities will consist of a two-story building of rectangular shape. The main KES building will be constructed at the existing location of the KES playground and baseball field. The new KES project also includes construction of supporting mechanical and electrical equipment yards, new sport fields, parking lots, a bus drop-off area, service access roads, fire lanes and covered walkways. Site layout for the proposed new KES is shown in Figure 3.

The KES main building will be a two-story reinforced concrete structure. Based on available as-built drawing information for the existing KES, the new KES main building will likely need some kind of soil improvement in order to support typical shallow footing foundations or alternatively, require deep foundations.

According to correspondence with Jacobs team designers, the proposed KES site elevation will be similar to the existing elevation of the baseball field. Therefore, cut and fill operations will be required during grading of the site. Slopes that result from earthwork operations are recommended to be covered by vegetation and to have a maximum slope of 2:1 (H:V).

Pavement structures at the site are expected to be flexible and rigid pavements composed of asphalt-concrete (AC) and plain concrete surfaces, respectively, subbase and base layers. Vehicle traffic will consist mainly of regular passenger cars, light pickup trucks and school buses.

Geotechnical Investigation Report 9

5.0 SITE CONDITIONS

5.1 SUBSURFACE CONDITIONS

A general description of the subsurface conditions and various soil materials encountered during our field exploration are presented in this section.

5.1.1 Subsurface Profile of the Site

Site soils consist mainly of surface fill layers of cohesive soils overlying soft to medium stiff clays followed by mudstone soils. The mudstone layer is considered the bedrock of the site.

Soils comprising the fill layers could be observed in test pits excavated for archeological investigation purposes conducted at the site by others. The size of the test pits were approximately 3 m x 3m x 3m. Fill soils at the site are typically composed of a mixture of clay and mudstone soils occasionally interspersed with gravel particles and construction debris such as crushed concrete pieces and medium to large sized rocks. Soil materials and grade of compaction are not consistent throughout the fill layer. There are no records available for the placement of this fill since it was probably dumped during past construction activities at the site. Thickness of this undocumented and uncontrolled fill vary throughout the site. For instance, at the central portion of the site, in between the existing playground area and the baseball field, the thickness of fill soil layers range from 2 to 6 m. Based on the distribution of the fill layers and the presence of soft alluvial clays, it is assumed that a former ravine was located crossing the central area of the proposed new KES, from south to north. The thickness of fill soil layers at the existing parking lot and the easternmost and southernmost areas of the site are relatively thin, ranging from 0.5 to 1 m. Underlying the fill soils, natural soft to medium stiff clay soils with high plasticity and mudstone bedrock layers with stiff to hard consistencies were observed.

The mudstone bedrock layer is considered a candidate bearing layer to support the foundations of the new KES structures.

Distribution of the site subsurface soils can be referenced in soil profiles included in Appendix B of this report.

5.1.2 Groundwater

Groundwater was observed in some of the soil boring locations. At borings conducted where the new KES is planned , the groundwater was detected at shallow depths (within 1.5 m bgs). At boring B-10 which was conducted at the most elevated area of the site (in the vicinity of the housing towers), groundwater was detected at 4.5 m bgs.

Groundwater detected at shallow depths is not considered a reliable indication of the natural ground water elevation of the site. Water levels encountered are likely the result of accumulation of water after rain events. However, it is assumed that the water elevation encountered at boring B-10 is a more reliable indication of the natural ground water level at the site. At this location, groundwater was noted to be located above the top of the mudstone bedrock.

Geotechnical Investigation Report 10

This elevation (approximately 26 m above MSL) coincides with the middle portion of the vegetated slopes located at the south portion of the site. In addition, at the south easternmost portion of the site, damp soils were observed at the toe of the slopes, which may indicate that groundwater is discharging at this elevation.

Fluctuations of groundwater level could occur due to change in seasons and variations in rainfall.

For instance, during rainy seasons, groundwater likely perches within the existing fill, above the top of the mudstone bedrock. Therefore, care shall be taken during the construction phase for controlling ground water accumulation in trenches, excavations and pits.

5.1.3 Subsurface Variations

Based on results of the subsurface exploration and our experience, some variations in the continuity and nature of subsurface conditions within the project site should be anticipated. Due to uncertainties in the nature and depositional characteristics of the earth material at the site and the variable nature of fill material placement at the site, caution and engineering judgment must be exercised in interpolating or extrapolating subsurface conditions between or beyond the boring locations.

5.2 GEOLOGICAL SITE HAZARDS

Screening for geological site hazards, including susceptibility to liquefaction, slope failure, settlement and corrosive environments, was conducted at the existing KES Site.

5.2.1 Soil Liquefaction

Liquefaction is defined as the phenomenon in which a cohesionless (generally sand) soil mass, within approximately 20 m of the ground surface, suffers a substantial reduction in its shear strength, due to the development of excess pore pressures. During earthquakes, excess pore pressures in saturated soil deposits may develop as a result of induced cyclic shear stresses, resulting in liquefaction. Soils that are most susceptible to liquefaction are clean, loose, saturated, uniformly graded, fine-grained sands that lie below the groundwater table within a depth of consideration ranging from 0 to 20 m below the ground surface. Based on the soil exploration conducted for this contract, site soils consist mainly of soft to medium stiff clays and mudstone soils throughout the site. Due to the relative absence of saturated sands and/or coarse silts in observed subsurface soils, the potential for liquefaction at the site is low. As a result, laboratory testing and detailed modeling analysis specific to liquefaction is considered inappropriate for the KES site.

Geotechnical Investigation Report 11

5.2.2 Potential Slope Failures and Settlement

The existing KES site is relatively flat and is located in a flat terrace area at an approximate elevation of 22 m above MSL. A topographic survey conducted by ESC between August and September 2014 indicates that the elevation difference between the site and surrounding areas is approximately 4 to 7 m. Existing retaining walls and slopes support the higher terrace area of the site. Retaining walls are located at the southwest and north portions of the site. Vegetated 2:1 (H:V) slopes are located to the south of the site and slopes with dense vegetation are located at the north and west portions of the site.

Slope failure was observed at the south portion of the site between the playground and baseball field, where vegetated 2:1 (H:V) slopes were constructed to accommodate the grading of the current KES site. It is suspected that the failure occurred due to groundwater variations after rainfall events. New retaining walls proposed in this area will contribute to stabilizing these slopes.

Settlement and consequent lateral ground movement were observed at the north portion of the site, at the boundary fence of the Camp Foster installation. This area is adjoining a steep slope that does not present signs of failure. However, settlement and lateral ground movement are affecting nearby structures. For instance, along the fence line, fence posts and light poles are tilting, and cracks and subsidence in concrete sidewalks can be observed. Similarly, an existing concrete block retaining wall shows displacements on the order of 50 to 100 mm. The foundations for the new KES are adequately isolated from the slope (distance between face of footings and edge of the slope are at least 2 times the width of the footing and 1/3 of the height of the slope) and supported by improved soils. Therefore, settlement or lateral movement that might affect the building foundation is likely to be negligible. However, ground reinforcement needs to be considered for the new fire lane road planned in this area.

5.2.3 Corrosive Soil Environments

In addition to standard soil laboratory testing, environmental laboratory analyses were conducted for cohesive soil samples taken at representative soil layers in order to determine the corrosion potential of site soils. Testing was performed by Okinawa Environmental Analysis Center, a certified environmental laboratory located in Okinawa. The following table summarizes test results for corrosivity of soils.

TABLE 1: WATER SOLUBLE CONSTITUENTS & SOIL CONDUCTIVITY

Constituent Units B-1

(1.15~1.45 m bgs) Cohesive Fill Soils

B-5 (2.15 ~2.45 m bgs)

Clay soils

B-7 (1.15~1.45 m bgs)

Mudstone soils

Water soluble chlorides mg/kg 17.0 8.0 7.5 Water soluble sulfates mg/kg 750 75 830 pH - 8.2 8.0 8.6

Soil conductivity mS/m 28.8 7.12 27.0

Soil Resistivity Ohm-cm 3,472 14,045 3,704

Geotechnical Investigation Report 12

The Soil Investigation Testing Result Interpretation and Analysis Manual published by the Japanese Geotechnical Society (JGS) (JGS, 1979) describes corrosive environments as those with the following characteristics:

a) Soil with soil conductivity values of greater than 200 mS/m

b) Soil with total chlorides exceeding 1mg/g (1000 mg/kg)

c) Soil with total sulfates exceeding 0.5mg/g (500 mg/kg)

d) Soils with pH values below 6 or over 9

Similarly, the US National Association of Corrosion Engineers (NACE) provides guidelines for soil corrosivity ratings as indicated in the table below.

TABLE 2: CORROSIVITY RATINGS ACCORDING TO NACE GUIDELINES

Soil Resistivity (ohm-cm)

Corrosivity Rating

>20,000 Essentially non-corrosive 10,000 to 20,000 Mildly corrosive

5,000 to 10,000 Moderately corrosive

3,000 to 5,000 Corrosive

1,000 to 3,000 Highly corrosive

<1,000 Extremely corrosive

Environmental test results indicate that surface cohesive fill and mudstone soils may be corrosive.

Clayey soils may be considered mildly corrosive according to the US National Association of Corrosion Engineers (NACE) guidelines.

5.3 SITE CLASS DESIGNATION

Field investigation and laboratory test results indicate that the site soils fit the Site Class “D” designation for seismic considerations. The hard mudstone bedrock which presented SPT N-values greater than 50 and was encountered within the top 30 m of soils were factors in selecting a Site Class “D” designation for the KES site.

Geotechnical Investigation Report 13

6.0 FIELD EFFORT

6.1 SOIL BORINGS AND STANDARD PENETRATION TESTING

Non-core soil borings and SPT were conducted at the site, using a Model NS-75G Yanmar drilling rig equipped with 66-millimeter diameter tube bit and split spoon sampler. In total, 14 soil borings at were conducted at the site, each conducted to variable depths to confirm the depth of the bedrock at the site, with SPTs performed per each meter drilled. Exploratory bore holes were placed in locations covering the future new KES building footprint and its supporting facilities. Refer to Figures 2 and 3 and the following Table 3 that shows the boring locations, depths and their relation to the new proposed KES facilities .

All soil borings terminated at depths where the hard mudstone deposits were encountered. The mudstone layer is considered the bedrock of this site, with SPT N-values no less than 50.

SPT N-values were evaluated along with soil testing data to provide foundation recommendations for the new KES facilities. Foundation recommendations can be found in Section 7.1 of this report.

Soil boring locations can be referenced in Figures 2 and 3 in Section 2.0 of this report.

In addition, 7 shallow hand auger borings to a depth of 1 m bgs were conducted in order to obtain soil samples for CBR testing to provide pavement recommendations. Pavement recommendations can be found in Section 7.3 of this report. CBR sampling locations and proposed pavement areas for the new KES can be referenced in Figure 7 of this report.

Boring logs and soil laboratory test results are included in the report appendices.

Geotechnical Investigation Report 14

TABLE 3: SOIL BORINGS SUMMARY

Soil Boring

Top of borehole elevation (m MSL)

Depth of boring (m bgs) Purpose of soil boring

B-1 23.45 12.36 Determine bearing layer and soil capacities for the new proposed KES main building structure and north side slope stability.

B-2 23.95 10.35

Determine bearing layer and soil capacities for the new proposed KES main building structure.

B-3 23.73 8.43

B-4 23.87 12.32

B-5 24.06 10.38 Determine bearing layer and soil capacities for the new proposed KES main building structure, new mechanical yard and electrical transformers pads.

B-6 22.84 7.37

Determine bearing layer and soil capacities for the new proposed KES main building structure, underground water tank, service entrance canopy, new mechanical yard, electrical transformers pads. and pedestrian bridge foundations.

B-7 22.83 7.35 Determine bearing layer and soil capacities for the new proposed KES main building structure and covered walkway.

B-8 23.04 12.33 Determine bearing layer and soil capacities for the new proposed KES main building structure.

B-9 21.97 6.38 Determine soil properties at new proposed parking lot area.

B-10 30.76 9.44 Determine bearing layer and soil capacities for the new proposed bus drop-off canopy.

B-11 22.09 6.39 Determine soil properties for new proposed open play area.

B-12 21.92 8.33 Determine bearing layer and soil capacities for the new proposed covered walkway.

B-13 22.86 12.29 Determine bearing layer and soil capacities for the new proposed KES main building structure.

B-14 22.54 7.34 Determine bearing layer and soil capacities for the new proposed KES main building structure and gym canopy.

Geotechnical Investigation Report 15

6.2 SOILS LABORATORY TESTING

Eight disturbed and seven undisturbed soil samples were taken at representative cohesive and granular soil layers at selected boring locations. Soils encountered at the site consisted mainly of soft to medium stiff clays followed by hard mudstone soil layers. Granular soils were encountered only at the most elevated portion of the site at boring B-10. Disturbed and undisturbed samples were extracted using the SPT split spoon sampler and a thin-wall sampler, respectively. Samples of typical layers were tested in the laboratory in accordance with relevant Japan Industrial Standard (JIS) and Japan Geotechnical Society (JGS) testing procedures, as follows:

TABLE 4: SOIL LABORATORY TESTING SUMMARY

Boring No. / Depth (m) bgs Soil Type

D en sit y of S oi l

So lid

P ar tic le s (J

IS

A

2)

So il

M oi st ur e C on te nt

(J

IS

A

3)

So il

Pa rt ic le

S iz e D ist ri bu tio n

A

4)

A

3)

A tte rb er g L im its

A

5)

C on so lid at io n T es t

(J

IS

A

U nc on fin ed

C om pr es sio n

T es t (J

IS

A

B-2 / 2.0~3.0

CH, Fat Clay

B-2 / 7.0~8.0

CH, Fat Clay

B-4 / 5.0~5.8

CL, Lean clay w/sand

B-5 / 2.0~2.8

CH, Fat Clay w/sand

B-7 / 1.0~2.0

CH, Fat Clay

B-10 / 2.0~3.0

CH, Fat Clay

B-10 / 4.0~4.5

GM, Silty gravel with sand

B-12 / 2.0~2.8

CL, Lean Clay with Sand

Notes: ○Indicates laboratory test has been conducted.

A summary of test results and soil laboratory test reports can be referenced in Appendix C of this report.

Geotechnical Investigation Report 16

7.0 CONCLUSIONS & RECOMMENDATIONS

7.1 FOUNDATION AND FLOOR SLAB RECOMMENDATIONS

7.1.1 KES Main Building

Based on the investigation, in order to implement a shallow foundation system for the new KES facilities, soil improvement is required at areas where soft/medium stiff clays and thick layers of undocumented fills are encountered at the site. In order to provide adequate support, soil improvement should be extended to a depth where mudstone bedrock layers are located.

Shallow and deep soil mixing systems consisting of soil-cement slurry and soil-cement columns, respectively, are recommended as soil improvement methods for this project. For locations where the mudstone bedrock bearing layer is located within 4 m of the new finished grade, soil improvement by means of soil-cement slurry is recommended. Soil-cement columns are recommended for locations where the mudstone bedrock bearing layer is located at depths greater than 4 m below finish grade.

Recommended allowable bearing pressures for shallow foundations with soil improvement are recommended to be 300 KN/m2. An increment of 1/3 of this allowable bearing pressure can be considered for short-term loads such as earthquake and short-time wind loads. In order to achieve the recommended bearing pressures, soil improvement must extend to depths where mudstone layers with SPT N-values greater than 30 are encountered. For cost estimating purposes, an average soil-cement column length of approximately 7 meters may be assumed, considering a minimum depth of penetration for footings of 1 m below finished grade. In addition, soil-cement columns are expected to be between 1,000 and 1,200 mm in diameter. Minimum design compressive strength for soil-cement columns and soil-cement slurry should be 1,400 KN/m2 and 900 KN/m2, respectively. Required cement amount is calculated to be approximately 400 kg/m3 for soil-cement columns and 350 kg/m3 for soil-cement slurry. For both cases water-cement ratio is 70%.

Construction considerations for soil improvement are included in Section 8.5 of this report.

The estimated total settlement of shallow foundations with soil improvement resting in mudstone layers based on the above conditions, and using columns loads provided by Jacobs, is calculated to be less than 25 mm. Estimated differential settlement is calculated to be less than 10mm.

Graphical representations of the target bearing layer are shown in soil boring logs and soil profiles included in Appendix A and B, respectively.

Regarding floor slabs recommendations, the uncertainty of fill soils quality and engineering behavior, inconsistency of material distribution and grade of compaction, and variation in thickness of the undocumented fill covering the central portion of the proposed new KES may lead to excessive differential settlement, which can affect the performance of a conventional slab-on-grade.

Geotechnical Investigation Report 17

For example, the north portion of the site, where settlement is affecting structures along the fence line, is comprised of fill soils. Furthermore, since this area has not been designated to support main structures (this portion of the site is currently occupied by the playground and baseball field), it is suspected that proper care was not taken when selecting and placing fill soil materials.

This undocumented fill underlies more than half of the footprint of the proposed new KES and has a depth of 4 meters on average. Based on these conditions, complete removal of this fill layer and consequent replacement with satisfactory materials is considered very costly. Therefore, a structural slab is recommended for the KES facilities.

Figure 5 shows the approximate coverage area of the undocumented fill at the site. In addition, expected areas for footings supported by soil-cement slurry and footings supported by soil-cement columns for the KES main building are shown.

In order to provide adequate support during construction of the floor slab, a 300 mm thick layer of imported granular fill underneath the floor slab is recommended. Recommended materials for locally available imported granular fill should be mechanically stabilized materials such as JIS standardized M-40 (or its recycled equivalent, RM-40), as shown in Figure 6 of this report, and should be inorganic, non-expansive and free of debris. The imported granular layer should be compacted to a minimum of 95 percent compaction as determined by ASTM D1557 or equivalent

JIS A1210.

To protect the floor slab against moisture, placement of a vapor barrier in between the floor slab and the imported granular fill layer should be considered by the design engineer. In addition, the top 100 mm of the recommended 300 mm thick layer of imported granular fill underneath the slab should consist of clean gravels in order to alleviate capillary action in the case of fluctuations in ground water. Recommended soils for clean gravel materials are JIS standardized S-20 or S-40 soils, as shown in Figure 6 of this report. The top 300 mm of subgrade soils or fill soils underneath the imported granular fill layer shall be compacted to a minimum of 95 percent in the case of granular soils or 90 percent in the case of cohesive soils.

Since radon mitigation systems were observed in some facilities within the Camp Foster installation, and in the case of installation of new radon mitigation systems under the floor slab for the new KES, it is appropriate to change the imported engineered granular fill material to an uniformly graded clean gravel with an appropriate layer thickness which accommodates radon mitigation system piping. For floor slabs which will have radon systems installed underneath, a Type 2 gas permeable gravel layer in accordance with Table 2 of ASTM E1465-08a is recommended (ASTM C33 #6 soil or JIS standardized S-20 or S-40 soils as shown in Figure 6).

The particle size of these clean gravels will depend on the size of the holes of the perforated radon piping and it should be coordinated with the radon mitigation system designer. The layer thickness shall be 200~300 mm thick or as applicable to accommodate radon piping systems. Subgrade soils or fill soils under this layer should be compacted as stated earlier in this section. Because uniformly graded clean gravel is designed to provide void space for radon mitigation purposes, it is difficult to provide a test based compaction requirement for this layer. However, appropriate construction

Geotechnical Investigation Report 18 quality control methods such as visual inspection and validation through inspections and/or tests, etc. shall be conducted during the placement and compaction of this radon system material layer.

Laboratory testing results indicate moderate expansion potential for disturbed mudstone soils.

Therefore, where the mudstone layers are encountered at shallow depths, care shall be taken in order to avoid excessive disturbance of mudstone soils during earthwork operations.

Resistance to lateral loading may be provided by friction acting at the base of shallow foundations, and by passive earth pressure acting on the buried portions of shallow foundations and grade beams.

A coefficient of friction of 0.40 can be considered acting between the spread footings and the soil-cement columns or soil-cement slurry. Passive earth pressure may be computed as an equivalent fluid having a density of 30 KN/m3.

Geotechnical Investigation Report 19

Figure 5: Approximate Areas of Undocumented Fill and Soil Improvement– KES Main Building

Geotechnical Investigation Report 20

7.1.2 KES Auxiliary Facilities and Other Structures

Based on the proposed KES plans provided by Jacobs, auxiliary facilities for the new KES such as electrical transformers pads, a mechanical equipment yard, covered walkways, canopies, a pedestrian bridge and an underground water tank are planned in conjunction with the KES main building. Figures 3 and 5 indicate the approximate locations of these auxiliary facilities and other structures.

For the electrical transformers pads, mechanical equipment yard, the service entry canopy and the pedestrian bridge which will be located at the south portion of the site adjacent and nearby to the new retaining walls and for the gymnasium canopy which will located at the west side of the KES main building, shallow foundations without soil improvement may be designed for an allowable bearing pressure of 100 KN/m2.

If large loads are imposed by these structures and larger bearing pressures are required, soil improvement can be implemented assuming similar capacities and installation requirements indicated for soil improvement for the KES main building.

For the covered walkway which will be located at the west side of the KES site, due to the presence of very soft clays, in order to support shallow foundations soil improvement is recommended.

Recommended allowable bearing pressures for shallow foundations with soil improvement are recommended to be 300 KN/m2. Similar to the KES main building, in order to achieve the recommended allowable bearing pressure, soil improvement must extend to depths where mudstone layers with SPT N-values greater than 30 are encountered.

Soil-cement columns of approximately 6 m length may be required for the westernmost portion of the covered walkway and since the mudstone bearing layer becomes shallower towards the east, soil-cement slurry may be required for the area near the gymnasium canopy and the KES main building.

For the underground water tank which will be located inside the KES main building and adjacent to boring B-6, an allowable bearing pressure of 150 KN/m2 may be used for the design of the concrete slab foundation. Based on communication with Jacobs design engineers, the bottom of this tank will be placed between 4 to 5 m below the finish grade. Water tank walls may be designed assuming at rest earth conditions since the walls will be restrained by the floor slabs. At rests earth pressure may be computed as an equivalent fluid having a density of 14 KN/m3. If movements of the walls on the order of 0.01 to 0.02 times the height of the wall are allowed, active earth pressures can be used. In that case, active earth pressure may be computed as an equivalent fluid having a density of 11.5 KN/m3. In addition, a minimum horizontal clearance of 1.5 m between the edge of surrounding footings and the water tank walls is recommended in order to avoid exerting additional pressure on the walls. Although, mudstone soils are expected to be exposed during excavation in the vicinity of the water tank area, mudstone soils should not be used as backfill material against the walls.

Footings should be a minimum of 1 m in width, and embedded at least 1 m below the finished grade. A recommended modulus of subgrade reaction of 27 MN/m3 may be used for the design of the slab-on-grades.