USACE_FTG217_GDR_FINAL.pdf

FINAL SUBMITTAL

REVISION 0

GEOTECHNICAL DATA REPORT

FTG217, MISSILE FIELD 4

FORT GREELY, ALASKA

CONTRACT NO. W911KB-17-D-0001

DELIVERY ORDER NO. 0008

PREPARED BY: PREPARED FOR:

U.S. ARMY ENGINEER

DISTRICT, ALASKA

CEPOA-EC-G-GM, MICHAEL ALLEY

2204 TALLEY AVE

JBER, AK 99506

R&M CONSULTANTS, INC.

9101 VANGUARD DRIVE

ANCHORAGE, AK 99507

5 JANUARY 2018

5 January 2018 R&M No. 2440.08

Mr. Michael Alley Contracting Officers Representative U.S. Army Corps of Engineers, Alaska District VIA EMAIL: mike.w.alley@usace.army.mil JBER, Alaska 99506

RE: Final Geotechnical Data Report FTG217, Missile Field 4, Fort Greely, Alaska IDIQ Contract for Geotechnical Design and Related Services

Contract No. W911KB-17-D-0001, Delivery Order No. 0008

Dear Mr. Alley:

Enclosed, please find our final geotechnical data report prepared for the above referenced project. This work has been completed in accordance with Contract No.

W911KB-17-D-0001, Delivery Order No. 0008. This final submittal includes review comments of the draft geotechnical data report made within ProjNet and distributed January 3, 2018.

We trust that this final report is found to be responsive to your requirements.

Should you have any questions or desire for additional information, please do not hesitate to call. It has been a pleasure to be of service to the USACE Alaska District on this effort.

Sincerely, R&M CONSULTANTS, INC.

Charles H Riddle, C.P.G.

Senior Vice President

GEOTECHNICAL DATA REPORT – FINAL USACE

FTG217, MISSILE FIELD 4 FORT GREELY, ALASKA

January 2018 Page i R&M No. 2440.08

GEOTECHNICAL DATA REPORT

MISSILE FIELD 4 (FTG217)

FORT GREELY, ALASKA

The following report presents the results of R&M’s geotechnical investigation completed to support design and construction of the programed Missile Field 4 (FTG217) project at Fort Greely, Alaska. The report includes discussion and results associated with R&M’s geotechnical subsurface exploration, and laboratory testing. The geotechnical engineering services performed by R&M Consultants, Inc. were authorized by the USACE under Contract No. W911KB-17-D-0001, Delivery Order No. 0008.

This report includes both factual and interpretative information and is intended to provide the project designers, construction inspectors, and construction contractors with a summary of the geotechnical conditions expected at the site, and to qualify a baseline for assessing changes in geotechnical conditions if or when they are suspected during construction. This report is intended solely for use by USACE and its contractors directly involved with FTG217 project design and construction; contingent upon the reader possessing basic understanding of geotechnical terminology and principles, as well as the referenced documents.

R&M consultants, Inc. has performed this work in a manner consistent with the level of skill ordinarily exercised by members of the profession currently practicing under similar conditions.

No warranty, express or implied, beyond exercise of reasonable care and professional diligence, is made. R&M’s services for the project were performed by, or under the responsible charge of the individuals listed below.

ROBERT M. PINTNER, P.E.

Senior Geotechnical Engineer

Aaron T. Banks, C.P.G Senior Geologist

REVIEWED BY:

CHARLES H. RIDDLE, C.P.G.

Senior Vice President

January 2018 Page ii R&M No. 2440.08

TABLE OF CONTENTS

Page Preface and Signatures ................................................................................................................................... i Table of Contents ............................................................................................................................................ ii List of Tables .................................................................................................................................................... iv List of Figures ................................................................................................................................................... iv List of Appendices ........................................................................................................................................... v Acronyms and Abbreviations ...................................................................................................................... vi Executive Summary ...................................................................................................................................... vii

Introduction

1.1 Background

1.2 Contract Authorization

1.3 Concept Plan

1.4 Scope-of-Work

1.5 Previous Investigations

1.5.1 R&M Consultants, 1999

1.5.2 R&M Consultants, 2000

1.5.3 R&M Consultants, 2001

1.5.4 Geomatrix Consultants, 1997

1.5.5 Geomatrix Consultants, 2001

1.5.6 USACE, 1994

1.6 Additional Technical Reports

1.7 Work Plan Deviations

Regional Setting and General Site Conditions

2.1 Regional Setting

2.1.1 Location

2.1.2 General Geology

2.1.3 Regional Seismicity

2.1.4 Climate

2.2 General Site Conditions

2.2.1 Topography

2.2.2 Surface Drainage

2.2.3 Vegetative Cover

2.2.4 Soils

2.2.5 Bedrock

2.2.6 Groundwater

2.2.7 Thermal Conditions

2.2.8 Geologic Hazards

TABLE OF CONTENTS (CONTINUED)

Page

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Investigation Methods

3.1 Test Boring and Resistivity Survey Positioning

3.2 Test Borings

3.3 Environmental Sampling

3.4 Inorganic Anion and pH Sampling

3.5 Backfilling

3.6 Percolation Testing

3.7 Thermistor Installation

3.8 Resistivity Testing

3.9 Downhole Seismic Testing

3.9.1 Seismic Sources

3.9.2 Seismic Testing and Data Reduction

3.9.3 Seismic Casing Abandonment

Laboratory and Field Testing Program Data Processing and Interpretation

5.1 Test Boring Logs

5.2 Relative Density

5.2.1 Geologic History

5.2.2 Sampler Penetration Counts

5.3 Determination of Groundwater

5.4 Determination of Thermal State of Soils

Geotechnical Conditions

6.1 Surface

6.2 Soil Conditions

6.2.1 Unit I – Glaciofluvial Outwash

6.2.2 Unit II – Glacial Margin and Buried Surficial Deposits

6.2.3 Unit IIIa – Silty Glacial Till Deposits (Brown)

6.2.4 Unit IIIb – Silty Glacial Till Deposits (Gray)

6.2.5 Unit IIIc – Glacial Till (Fluvial Gravel and Sand)

6.2.6 Unit IV – Fluvial Deposits

6.2.7 Cobbles, Boulders, and Erratics

6.3 Downhole Seismic Results

6.4 Bedrock Conditions

6.5 Groundwater Conditions

6.5.1 Percolation Test Results

6.6 Thermal Conditions

6.7 Soil Resistivity Results

6.8 Environmental Considerations

Conclusions References

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LIST OF TABLES

Table 2-1: Big Delta Climatological Data Table 3-1: Summary of R&M Test Borings AP-2879 through AP-2906, FTG217 Table 3-2: Summary of R&M Test Borings AP-2907 through AP-2924, FTG217 Table 3-3: Inorganic Anion and pH Testing Locations Table 4-1: Laboratory and Field Analysis Methods Table 6-1: Compilation of 2017 Investigation at FTG217 Laboratory Test Results Table 6-2: Compilation of Historic Fort Greely NMD Laboratory Test Results (1998, 1999, and 2000) Table 6-3: Percolation Test Results Table 6-4: Summary of Ground Temperature Measurements, Test Boring AP-2883 Table 6-5: Summary of Ground Temperature Measurements, Test Boring AP-2897 Table 6-6: Summary of Soil Resistivity Testing, FTG217

LIST OF FIGURES

Figure 1-1: Fort Greely Regional Area Map Figure 2-1: Known Seismic Sources in the Fort Greely Area Figure 2-2: Diagrammatic Cross-Section of Permafrost and Groundwater in the Big Delta Area Figure 3-1: Drilling and Site Conditions Photographs Figure 3-2: Drilling and Site Conditions Photograph Figure 3-3: Typical Thermistor Installation Figure 3-4: Soil Resistivity Testing Photograph Figure 3-5: Downhole Seismic Velocity Survey Method Figure 6-1: Unit I, Glaciofluvial Outwash Photograph Figure 6-2: Unit II, Glacial Margin and Buried Surficial Deposits Photograph Figure 6-3: Unit IIIa, Silty Glacial Till (Brown) Deposits Photograph Figure 6-4: Unit IIIb, Silty Glacial Till (Gray) Deposits Photograph Figure 6-5: Unit IIIc, Glacial Till (Fluvial Sands and Gravels) Deposits Photograph Figure 6-6: Unit IIIc, Glacial Till (Fluvial Sands and Gravels) Deposits Photograph Figure 6-7: Plotted Results of Ground Temperature Measurements, FTG217 Figure 6-8: Plotted Results of Soil Resistivity Testing, FTG217

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LIST OF APPENDICES

Appendix A – Site Maps Location and Vicinity Map ....................................................................................................................... A-01 Area Map ...................................................................................................................................................... A-02 Surficial Geologic Map ............................................................................................................................. A-03 Test Boring Locations ............................................................................................................................... A-04 Generalized Geologic Cross Sections .............................................................................. A-05 thru A-07

Appendix B – Test Boring Logs General Notes .............................................................................................................................................. B-01 Explanation of Selected Symbols ......................................................................................................... B-02 Test Boring Logs AP-2879 thru AP-2924 .......................................................................... B-03 thru B-97

Appendix C – Laboratory Testing Results Classification of Soils for Engineering Purposes ASTM D 2487 ................................................... C-01 Frost Design Soils Classification ........................................................................................................... C-02 Summary of Laboratory Soils Data ................................................................................... C-03 thru C-48 Gradation Curves ................................................................................................................... C-49 thru C-119 Atterberg Plots ...................................................................................................................... C-120 thru C-123

Appendix D – Downhole Seismic Survey Downhole Seismic Survey Report ................................................................................................... 8 Pages

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ACRONYMS AND ABBREVIATIONS

˚F degree Fahrenheit AP auger point ASTM ASTM International avg average bgs below ground surface B.P. before present CME Central Mining Equipment Company DWG drawing EPA Environmental Protection Agency FTG217 Fort Greely Missile Field 4 GDR geotechnical data report GIS geographical information system GPR ground penetrating radar I.D. inside diameter in inches LPT large penetration test M moment magnitude, unless noted otherwise MEB mechanical electrical building MHz Megahertz mm millimeter NAD83 North American Datum of 1983 NAVD88 North American Vertical Datum of 1988 NMD National Missile Defence O.D. outside diameter P4 Percent passing No. 4 sieve P200 Percent passing No. 200 sieve P.02 Percent finer than 0.02 mm P-wave compression wave PID photoionization detector ppm parts per million psf pounds per square foot PVC polyvinyl chloride QEP qualified environmental professional R&M R&M Consultants, Inc.

S-wave shear wave SEP subsurface exploration plan SOW Statement of Work SPT Standard Penetration Test USACE United States Army Corps of Engineers USCS Unified Soil Classification System USGS United States Geologic Survey WGS84 World Geodetic Survey 1984 WRCC Western Region Climate Center

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EXECUTIVE SUMMARY

The U.S. Army Corps of Engineers, Alaska District (USACE) has conducted a geotechnical investigation to provide design information for constructing Missile Field 4, located on the east side of the existing Missile Fields 1 through 3 within Fort Greely, about 5.5 miles south of Delta Junction, Alaska. R&M Consultants, Inc. (R&M), under contract with the USACE, performed a geotechnical field investigation at the site during the period of 30 October through 23 November 2017. The geotechnical investigation was performed concurrently with an USACE managed environmental investigation, reported under separate cover by the USACE. The geotechnical investigation included the drilling of test borings, sampling, laboratory testing, in-situ soil resistivity testing, and downhole seismic velocity testing.

This current report builds on data and interpretations derived from 1998, 1999, and 2000 field programs at the adjacent Fort Greely NMD site, along with new data and interpretations derived from this most recent November, 2017 field program. Especially significant was determination of the characteristics and index properties of the site soils at the Missile Field 4 site. This report presents a summary of results from R&M’s field subsurface exploration program and our interpretation of geotechnical site conditions.

It is understood that development at the Missile Field 4 site will include construction of approximately 20 silos, which would house ground-based interceptor missiles, and an associated mechanical and electrical building. The investigated site is approximately 100 acres in area and is located on a broad, gently sloping outwash plain between about Elevation 1,345 and 1,355.

The test hole program and geophysical surveys conducted during the Missile Field 4 field investigation provides site-specific information for the purposes of site design and planning. A total of 46 test borings were drilled and sampled. In selected borings, casing was installed for downhole geophysical surveys and ground temperature monitoring in other borings. Laboratory testing of soil samples obtained during the field program was also undertaken for the purposes of material classification and obtaining soil index properties of materials encountered. All were obtained to derive technical data useful for engineering application and geotechnical interpretation of site conditions.

Soils encountered at the site are interpreted as glaciofluvial outwash deposits which were formed on a relatively level floodplain of a stream flowing from a glacier. The material is described as moderately well-stratified layers and lenses of well-rounded, poorly to moderately well-sorted silty or sandy gravel with lenses of well-sorted sand. Numerous cobbles and boulders were encountered within the test borings. Glacial till and a lower fluvial/outwash deposit were interpreted to underlie the glaciofluvial material. In general, the downhole seismic velocity survey agrees well with the interpretation of the soils encountered during the test boring program.

No bedrock was encountered during our geotechnical site investigation. On the basis of currently available information, it appears that bedrock is located at a considerable depth beneath the site.

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Groundwater was not encountered within any of the test borings. On the basis of currently available information, it appears that any long-term hydrostatic water table is located at a considerable depth beneath the project site. Thus, it is not expected that long-term water table conditions would be involved in any construction considerations. However, perched groundwater, may be encountered in shallow on-site excavations, depending on specific location and time of year.

Permafrost was also not encountered within any of the test borings. However, in this general area, permafrost is considered sporadic and the possibility does exist that isolated areas of permafrost could be encountered during future construction. No on-site or subsurface contamination was observed via field screening methods during the course of our field investigation.

Comparison of existing geotechnical data from the existing and adjacent Fort Greely NMD site to data collected during this current FTG217 geotechnical investigation indicate that subsurface conditions are generally consistent between the two sites.

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INTRODUCTION

The U.S. Army Corps of Engineers, Alaska District (USACE) contracted R&M Consultants, Inc. (R&M) to complete a subsurface exploration program and prepare a geotechnical data report for the FTG217 project. This document is the FTG217 Geotechnical Data Report (GDR).

Site descriptions and subsurface conditions presented herein are based on our current understanding of the project and location as outlined within and illustrated on the drawings included in the appendices to this report. Any deviation from the proposed location would necessitate further evaluation of subsurface conditions.

1.1 BACKGROUND

USACE is presently conducting a geotechnical investigation to provide subsurface information for constructing Missile Field 4 (FTG217) to support additional missile defense capacity at Fort Greely, Alaska. Work consisted of geotechnical drilling, sampling and laboratory testing, soil resistivity testing and downhole seismic velocity testing. It is understood that geotechnical data gained from this investigation will be used in developing the design criteria and specifications for the project.

This report presents the results of the field investigation and our interpretation of site conditions.

Figure 1-1 provides a regional map of Fort Greely.

1.2 CONTRACT AUTHORIZATION

This study has been conducted under the terms of Contract No. W911KB-17-D-0001 between the USACE and R&M. This report is in specific fulfillment of Delivery Order No. 0008 of the contract.

Measurements and weights presented in this report are generally shown as U.S. Customary Units.

1.3 CONCEPT PLAN

Development at the FTG217 project site is understood to include construction of 20 subsurface missile silos, an MEB structure and other site improvements. The proposed silo facility footprint is approximately 1,250 feet by 350 feet in dimension while the Mechanical Electrical Building (MEB) structure footprint is approximately 135 feet by 90 feet in dimension. Other than a proposed silo and building locations, no other design information is currently available.

The proposed Missile Field 4 site layout is presented on Drawing A-04 in Appendix A.

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FIGURE 1-1: FORT GREELY REGIONAL AREA MAP

1.4 SCOPE-OF-WORK

The intent of this geotechnical investigation is to gather data on geologic and geotechnical conditions that could affect site planning, design, and construction of the proposed Missile Field 4.

The investigation provides specific geotechnical design information for earthwork, utility design, January 2018 Page 3 R&M No. 2440.08 and construction at the proposed facilities. Geotechnical activities in support of the FTG217 project were performed in accordance with standard procedures, as outlined in “Geotechnical Investigations” (USACE, 2001), and following the USACE’s Statement of Work (SOW) and the Subsurface Exploration Plan (SEP) prepared by R&M (R&M, 2017).

A Statement of Work prepared by USACE, dated 29 September 2017 and revised on 6 October 2017, summarizes the Scope-of-Work for this project. Work performed by R&M in support of this geotechnical effort consisted of the following:

• Provided supervision, labor, materials, tools, equipment and transportation necessary to perform the field work.

• Provided coordination of scheduling with USACE and Fort Greely personnel.

• Procured required permits, utility locates, and dig permit clearances.

• Prepared daily logs of field operations, observations, and measurements; and compiling these logs for final reporting.

• Performed a soil resistivity survey.

• Provided a subcontract drilling contractor.

• Provided a geophysics subcontractor to perform downhole seismic survey.

• Provided supervision of drilling, soil sampling, backfilling and plugging of borings, moving between borings, and cleaning the work areas.

• Provided access to soil samples for USACE chemists/engineers to perform chemical sampling of soil.

• Provided preservation and transportation of soil samples, measurement of groundwater levels (not encountered) and soil temperatures, and preparation of soil test boring logs.

• Provided all supervision, labor, materials, tools, equipment, and transportation necessary to perform laboratory testing of soils.

• Provided draft geotechnical test boring logs from the 11 test borings around the proposed mechanical electrical building (MEB) by 1 December 2017.

• Prepared draft and final geotechnical data reports (GDR) presenting the results of drilling and sampling, laboratory testing, field methodology and operations, and data interpretation.

• Provided test boring locations via swing tie technique from surveyed points if locations are altered in the field (e.g. refusal, utility conflict).

Test boring depths and locations were specified by the USACE in the SOW.

1.5 PREVIOUS INVESTIGATIONS

A number of technical projects and regional-level studies have been performed in the area. The following paragraphs provide a summary of the pertinent technical projects. Detailed information from these prior investigations has not been repeated herein. The reader is referred to the previous reports for specific data (see Section 8.0).

1.5.1 R&M CONSULTANTS, 1999

R&M, under contract with the USACE, performed a preliminary geotechnical investigation during October through December of 1998 at the site of the proposed Fort Greely National Missile Defense Site (R&M, 1999a). As part of that preliminary site investigation, a total of five test

January 2018 Page 4 R&M No. 2440.08 borings of 100-foot nominal depth were drilled and sampled. The total footage drilled was approximately 497 linear feet. Additionally, borehole seismic velocity and borehole conductivity surveys were performed.

The work was intended to provide preliminary subsurface characterization as part of the site selection process. At the same time, a separate geotechnical investigation was performed at a proposed site on Fort Wainwright immediately adjacent to Eielson Air Force Base (R&M, 1999b).

The reports presented a summary of the results of R&M's field programs at the respective sites, our interpretation of soil conditions, and provided preliminary design recommendations for general earthwork, foundation construction, and other site development considerations.

1.5.2 R&M CONSULTANTS, 2000

During the period of August through November, 1999, R&M conducted a detailed geotechnical investigation at the Fort Greely NMD site (R&M, 2000). A total of 167 test borings were drilled ranging from about 8 to 101 feet deep. The total footage drilled was approximately 6,618 linear feet. Thirteen (13) test pits were also excavated during this phase of investigation. Borehole seismic velocity surveys were performed in ten of the borings and ground temperature measurements were conducted in another ten borings. In total, 13,110 feet of ground penetrating radar (GPR) data were acquired. The report presented a summary of the field data, our interpretation of site conditions, and conclusions and geotechnical design recommendations for the project as laid out at that time.

1.5.3 R&M CONSULTANTS, 2001

In early 2000, the Fort Greely NMD project layout was shifted and reconfigured. During the period of September through October, 2000, R&M conducted subsurface investigations to account for this shift and reconfiguration. A total of 92 test borings were drilled to provide specific geotechnical design information within areas that were deficient of data. The reporting effort also included compiling, summarizing and re-presenting the resultant data from the previous R&M reports from 1999 and 2000 (R&M, 2001).

1.5.4 GEOMATRIX CONSULTANTS, 1997

Geomatrix Consultants, Inc. conducted a study in 1997 as part of a geologic evaluation of Fort Greely. The evaluation was conducted to: 1) assess earthquake ground motions at the installation;

2) assess seismic-geologic hazards that could pose a substantial life safety risk at the installation, including the hazards of surface-fault rupture, soil liquefaction, soil differential compaction, landsliding, and earthquake-induced flooding; and 3) assess the site classifications required for seismic structural screening evaluations (Geomatrix, 1997).

1.5.5 GEOMATRIX CONSULTANTS, 2001

Geomatrix Consultants, under contract with the U.S. Army Engineer Division, Huntsville, Alabama and URS Consultants, performed a seismic-geologic evaluation of the proposed Fort Greely NMD site. The seismic-geologic evaluation was comprised of two tasks: an assessment of the potential for seismic-geologic hazards (surface-fault rupture, soil liquefaction, differential compaction, landsliding, and flooding); and an evaluation of the potential for tectonic movement (uplift, subsidence, and tilting) at the proposed site (Geomatrix, 2001).

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1.5.6 USACE, 1994

The USACE performed a subsurface investigation for a landfill expansion project located approximately 5,500 feet south of the proposed Missile Field 4 site (USACE, 1994). During the period of July through September, 1993, six borings were drilled totaling 1,140 linear feet.

Predominant soil classifications were well to poorly graded gravel with silt and sand. Groundwater was encountered at approximately 280 feet below ground surface.

1.6 ADDITIONAL TECHNICAL REPORTS

A number of U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys documents as well as other technical reports were reviewed in regards to regional conditions.

These various reports are cited herein and listed in the references section of this report.

1.7 WORK PLAN DEVIATIONS

Deviations from the approved work plan occurred and are described below.

• During drilling of Test Boring AP-2879, the casing drive shoe became parted from the drill string and the borehole was shifted about 3 feet horizontally and re-drilled to total depth.

Complete details of abandoned tooling is provided on the test boring log.

• During drilling of Test Boring AP-2889, a portion of the drill string casing became parted from the drill string and the borehole was shifted about 2 feet horizontally and re-drilled to total depth. Complete details of this abandoned tooling is provided on the test boring log.

• During drilling of Test Boring AP-2912, no recovery of soils was achieved within the prescribed environmental sampling depth, so the borehole was shifted about 1 foot horizontally and re-drilled to total depth.

• Complete details of the aforementioned borehole shifts are provided on their respective boring logs provided in Appendix B.

• Falling head measurements were to be made using a digital pressure transducer, which records pressure readings and could later be downloaded for analysis. Once deployed at temperatures well below freezing, the pressure transducers failed to perform and the backup method of a water level indicator and stopwatch were utilized.

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REGIONAL SETTING AND GENERAL SITE CONDITIONS

2.1 REGIONAL SETTING

2.1.1 LOCATION

The project site is situated at Fort Greely which was formally established in September of 1941 and was named for arctic explorer A.W. Greely. The project site is located on U.S. Geological Survey (USGS) Mt. Hayes (D-4) Quadrangle, Township 11 South, Range 10 East, Section 13, Fairbanks Meridian, Alaska (USGS, 1991). The site is located at 63.9577 degrees North, and 145.7091 degrees West, in WGS84 decimal degree coordinates, based on Google Earth.

The site is approximately 1.5 miles south of the main cantonment area on Fort Greely and about

5.5 miles south of Delta Junction, Alaska (Figure 1-1). The Trans-Alaska Pipeline is located approximately 1 mile west of the proposed project site. Pipeline Pumping Station No. 9 is about 2.5 miles southwest of the site. The Richardson Highway (Alaska Route 4) is approximately 1.5 miles west of the site. The main entrance to Fort Greely is at about Milepost 261 of the Richardson Highway.

2.1.2 GENERAL GEOLOGY

The project area lies in the Tanana-Kuskokwim Lowlands physiographic province (Wahrhaftig, 1965). These lowlands are a broad depression bordered by the Alaska Range to the south and the Yukon-Tanana Uplands to the north and are generally characterized by glacial moraines, outwash plains, terraces and floodplains formed by glaciers and streams flowing northward from the Alaska Range.

This portion of east-central Alaska was covered with glacial ice during glacial advances of middle to late Pleistocene age (Coulter et al., 1965). This area is considered to generally be underlain by numerous isolated masses of permafrost (Ferrians, 1965 and Jorgenson et al., 2008); however, many locations on the north flank of the Alaska Range are free of permafrost. Both temperature of permafrost at depth just below the zone of seasonal variation, and air temperature are extremely variable in regions of discontinuous permafrost.

At least four Quaternary age glaciations have been identified within this region. The project area is known to have been reached by glacial ice from only two episodes (Delta and Donnelly glaciations). The Delta Glaciation is recognized by fairly well preserved, breached moraines on the north side of the Alaska Range. The Donnelly Glaciation is characterized by fresh knob and kettle topography (Péwé, 1965). The project site is located on glaciofluvial deposits of the Donnelly glaciation. Contacts from both glaciations are present in the project vicinity.

Geologic mapping has been published at a scale of 1:63,360 (1 inch equals 1 mile) by the U.S.

Geological Survey for the Mt. Hayes D-4 Quadrangle (Péwé and Holmes, 1964). Additionally preliminary engineering geologic maps of the Trans-Alaska Pipeline route have been prepared for the area (Weber, 1971). Péwé et. al (1969) present a discussion of the origin and paleoclimatic significance of large-scale patterned ground in the Donnelly Dome area. Although quite dated, Holmes & Benninghoff (1957) provide detailed information regarding terrain conditions in the Fort Greely area.

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Donnelly Dome is a prominent knob that is located about 12 miles south of the project site, and which rises to an elevation of 3,910 feet. Geologic evidence indicates that Donnelly Dome was overridden by a glacier, probably during the Delta Glaciation, which occurred perhaps 70 to 140,000 years B.P. The project site is at an elevation of 1,350 feet, approximately 2,560 feet lower than the top of Donnelly Dome. This fact, together with the fact that moraines assumed to be from the Delta Glaciation have been mapped nearly 20 miles north of the project site, is suggestive that at least during the Delta Glaciation, a significant thickness of glacier ice covered the site. Also the site was almost certainly subject to seismic shaking during the time it was covered by glacier ice. These two factors, separately or individually, likely account for the high degree of compactness noted throughout the glacial tills at the site.

Previous investigation in the project vicinity encountered granular soil deposits covered by silt, silty soils, and organics that were generally 0.5 to three feet thick. This surficial layer of silt and sandy silt to silty gravel is interpreted as a loess deposit (wind-blown silt). Granular soil was divided into four major units including an upper glaciofluvial outwash deposit; a unit composed of various glacial margin and buried surficial deposits; glacial tills; and finally a deposit that may be of fluvial origin to the depth explored. The investigation area for this project is surficially mapped as glaciofluvial deposits from the Donnelly Glaciation (R&M, 2001, Reger et al., 2008).

2.1.3 REGIONAL SEISMICITY

The Tanana-Kuskokwim Lowlands is an active seismic region, characterized historically by frequent, moderate to strong (magnitude 5 to +7), shallow crustal earthquakes associated with convergence and subduction of the Pacific plate underneath the North American plate across southcoastal Alaska (Ruppert et al., 2008). In east-central Alaska, most of this tectonic convergence has been accommodated by right-lateral movements along the large-scale, strike-slip Denali and Kaltag-Tintina fault systems, respectively about 50 miles south and 100 miles north of the project (Ruppert et al., 2008). However, additional lesser movements have also been accommodated across the Tanana-Kuskokwim Lowlands within several north-northeast trending seismic zones, and a complex series of Quaternary thrust faults and folds along the northern Alaska Range foothills (Bemis et. al., 2012; Ruppert et al., 2008).

Figure 2-1 illustrates the known faults with Quaternary-age activity surrounding the project (Koehler, 2013). Referring to Figure 2-1, earthquakes have occurred within the last 150 years along the Denali fault about 50 miles south of the project, and the Salcha and Fairbanks Seismic Zones about 60 and 80 miles northwest of the project, respectively. Additionally, there are at least seven known faults with interpreted displacements during the last 12,000 years located within about 40 miles of the project, including the Donnelly Dome fault, Grant Mountain fault, McGinnis Glacier fault, Molybdenum Ridge fault, Panoramic fault, and two unnamed faults (Bemis et. al., 2012;

Koehler, 2013).

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FIGURE 2-1: KNOWN SEISMIC SOURCES IN THE FORT GREELY AREA

Red lines = historic faults or seismic zones (last displacement <150 years): Dc – Denali (central section). Brown lines = Holocene faults (last displacement <12k years): BC – Billy Creek, Ca – Canteen, DD – Donnelly Dome, MG – McGinnis Glacier, MR – Molybdenum Ridge, Pa

– Panoramic, un - unnamed. Yellow lines = late Pleistocene faults (last displacement <130k years): GM – Granite Mt., Re – Rex, RM – Red Mt., Tr – Trident. Purple lines = Quaternary faults (last displacement <1,600k years): Black lines = age of most recent displacement unknown. http://maps.dggs.alaska.gov/qff/#63.99885:-144.68170:9 (last accessed 11 December 2017)

Since the early 1900s at least 10 instrumented earthquakes of local (ML) or moment (M) magnitude greater than 6 have been cataloged1 within about 100 miles of the project; including earthquakes of ML7.3 in 1937 (about 60 miles west of the project), ML7.2 in 1947 (about 65 miles west of the project), and M7.9 in 2002 (along the Denali fault rupturing about 40 miles south of the project).

2.1.4 CLIMATE

The Fort Greely area experiences a sub-arctic climate subject to an interior continental climate regime, characterized by light precipitation, cold dry winters, and warm summers. Based on climate data recorded at the Big Delta weather station (500770): the mean annual air temperature is approximately 28.2 degrees Fahrenheit (°F), with minimum and maximum monthly averages of approximately -3.5 °F (January) and 60.0 °F (July), respectively. Daily extremes range from - 63 °F (January 1947) to 92 °F (June 1969). The area receives an average of approximately 11.30 inches of precipitation per year, with maximum monthly mean of approximately 2.62 inches in July (WRCC, 2017).

1 Alaska Earthquake Center: http://www.giseis.alaska.edu/Seis/

PROJECT

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January 2018 Page 9 R&M No. 2440.08

A summary of climatological data obtained from the Big Delta recording station is presented in Table 2-1.

TABLE 2-1: BIG DELTA CLIMATOLOGICAL DATA

Weather Station Parameter Big Delta AP (Station No. 500770)

Period of Record 1917 to 2016 Elevation (feet) 1,276

Mean Annual Temperature (°F) 28.2 Mean Maximum Annual Temperature (°F) 36.9 Mean Minimum Annual Temperature (°F) 19.5

Record High Temperature (°F) 92 (15 June 1969) Record Low Temperature (°F) -63 (30 January 1947)

Mean Annual Precipitation (inches) 11.30 Mean Maximum Monthly Precipitation (inches) 2.62 (July)

Maximum Daily Precipitation (inches) 2.27 (28 July 2008) Mean Annual Snowfall (inches) 43.8

Mean Maximum Monthly Snowfall (inches) 9.2 (October) Maximum Monthly Snowfall (inches) 41.8 (November 1994)

NOTES:

After Western Regional Climate Center (WRCC, 2017)

2.2 GENERAL SITE CONDITIONS

General site conditions at the FTG217 project site are described in the following sections.

2.2.1 TOPOGRAPHY

Topography at the site is generally flat and is located on a broad, gently sloping outwash plain with a site elevation of about 1,350 feet. The surface slopes toward the north at about 50 feet per mile (approximately 1 percent) within the project area. Notably, the elevation increases toward the south in the direction of Alaska Range foothills.

2.2.2 SURFACE DRAINAGE

Surface drainage is accomplished via sheet-flow or by percolation into underlying unfrozen soil.

Major streams in the area include the Delta River located approximately three miles west of the site and Jarvis Creek located approximately three miles east of the site. Both are braided streams, which indicates a general inability for the stream to fully carry typical water throughput. Jarvis Creek flows into the Delta River approximately five miles north of the site. According to Anderson (1970), the average annual runoff for the Delta River drainage is greater than 48 inches.

No seeps were observed in the project area. Additionally, other than ditches and occasional culverts, no drainage structures are currently in place along the roadways and/or firebreaks adjacent the project area.

2.2.3 VEGETATIVE COVER

Generally, the areas within and adjacent to Fort Greely are considered to be within the lowland spruce-hardwood forest biotic community (AEIDC, 1976). This biotic community consists of evergreen and deciduous trees dominated by black spruce which sometimes occurs in extensive

January 2018 Page 10 R&M No. 2440.08 pure stands. Rolling basins and knolls in the lowlands support varied mixtures of white spruce, black spruce, paper birch, aspen and balsam poplar. Bogs and muskegs occur on lower ground.

Understory includes willows, dwarf birch, berries, cotton grass and mosses.

A forest fire burned most of the vegetation on the site in mid-June of 1999. Prior to the forest fire, vegetative cover consisted of moderately open stands of balsam poplar, aspen, and white spruce to a height of approximately 10 to 20 feet with little to no understory. An earlier fire is reported to have occurred in the area approximately 95 years ago (Péwé, 1965). According to Viereck and Little (1972), following fire and a willow stage, fast growing aspen stands develop.

The project area is dominated by burnt and decaying stands of spruce, birch and poplar with a secondary regrowth of poplar.

2.2.4 SOILS

The following paragraphs present very general comments regarding regional-wide soil types.

Detailed discussion of soils encountered at the project site during R&M's subsurface investigations are provided in Section 6.

Surficial soils at the proposed Missile Field 4 site are interpreted as glaciofluvial outwash deposits (Péwé and Holmes, 1964 and Reger et al., 2008). The material is described as moderately well stratified layers and lenses of well-rounded poorly to moderately well-sorted unconsolidated light yellowish brown silty or sandy gravel with lenses of well-sorted sand; gravel consists mostly of gneiss, granitic rock, quartzite, and diorite.

Péwé and Holmes (1964) present the following general properties of glaciofluvial deposits in the region:

Drainage Surface drainage poor to good. Excellent permeability except locally in silt or where perennially frozen.

Permafrost Permafrost table more than 25 feet deep, except beneath silt mantled areas where it occurs from three to nine feet. Low ice content except in silt deposits.

Susceptibility to Frost Action Gravel unsusceptible; intense in fine fraction.

Bearing Strength and Slope Stability Bearing strength high except in local areas of silt and peat on the younger glaciofluvial deposits.

Steep slopes unstable.

Distribution and Thickness Widespread. Maximum thickness of about 150 feet exposed on Delta River.

Terrain and Natural Slopes Outwash aprons merge with moraines; little or no relief. Younger deposits form scattered low hills of till and glaciofluvial deposits.

January 2018 Page 11 R&M No. 2440.08

Seasonal Changes and Dynamic Processes Winter: discontinuous snow cover. Break-up: local flooding, especially in silt-filled swales. Summer and freeze up: moist to dry, varies with cover and rainfall.

Excavation and Compaction Easy to excavate and compact with power tools except where perennially frozen.

Possible Uses Excellent foundation for structures and aircraft landing sites. Excellent source of gravel for subgrade and base-course material, and, if crushed and screened, for road metal and concrete aggregate. Source of enormous quantities of groundwater.

Typical soil index properties for glaciofluvial outwash deposits in the region are reported by Kreig and Reger (1982) as follows:

• Moisture Content: 0 to 9.9 % , Avg. 3.5 %

• Dry Density: 110 to 160 pcf, Avg. 135 pcf

2.2.5 BEDROCK

Bedrock was not encountered in any of R&M's test borings drilled at the site nor has bedrock been encountered in any of the deep (approximately 300-foot) borings drilled for the adjacent landfill expansion project.

Precambrian rocks of the Birch Creek Schist Formation are exposed on Donnelly Dome (about 10 miles south of the site) and other locations south of Donnelly Dome. The name "Birch Creek Schist" has been applied to all of the older Precambrian metamorphic rocks of the area that are of sedimentary origin. Granodiorite of Mesozoic-age has also been intruded in the area of Granite Mountain. Additionally, Tertiary-age coal-bearing rocks are exposed south of Donnelly Dome (Wahrhaftig & Hickcox, 1955).

2.2.6 GROUNDWATER

Groundwater was not encountered within any test borings to the total depths explored. However the USACE did encounter groundwater at depths of approximately 280 feet below ground surface at the adjacent landfill expansion project (USACE 1994). Groundwater measurements indicated a flow in an east-northeast direction at a gradient of 0.0044. Groundwater within the main cantonment area of Fort Greely has been found at depths ranging from approximately 170 to 230 feet below ground and generally flows in a northeastward direction (USACE,1991). Note that the ground elevation of the main cantonment area is about 125 to 150 feet lower than the project site and the adjacent landfill expansion project. Figure 2-2 presents a diagrammatic cross-section of groundwater in the Big Delta area.

Wilcox (1980) indicates that well yields are as high as 1,500 gallons per minute from a well at Fort Greely. Wilcox further states that losses from the Delta River and Jarvis Creek are the main sources of recharge to the aquifer in the area

January 2018 Page 12 R&M No. 2440.08

2.2.7 THERMAL CONDITIONS

As previously mentioned, the region is considered to generally be underlain by numerous isolated masses of permafrost. However, many locations on the north flank of the Alaska Range are free of permafrost. Figure 2-2 presents a diagrammatic cross-section of permafrost in the Big Delta area.

The thermal conditions at the site were investigated by monitoring of the ground temperatures with thermistors. The results of the data accumulated led to a characterization of the site as being unfrozen. Sections 3 and 5 present information regarding on-site thermistor installations and resulting ground temperature data while further discussion of site thermal conditions is contained in Section 6.

FIGURE 2-2: DIAGRAMMATIC CROSS-SECTION OF PERMAFROST AND GROUNDWATER IN THE BIG DELTA AREA

Note: The water table shown in this diagrammatic cross-section depicts the regional aquifer. Perched groundwater should be expected at certain near-surface locations, depending on the time of year.

After Péwé and Reger, 1983.

2.2.8 GEOLOGIC HAZARDS

With the exception of earthquakes and the potential for isolated permafrost, there are no other known geologic hazards (e.g. flooding, avalanches, mass slope wasting, etc.). However, strong winds occur in the area, especially in the winter season.

January 2018 Page 13 R&M No. 2440.08

INVESTIGATION METHODS

Methods of investigation for the FTG217 geotechnical field investigation are described in the following sections.

3.1 TEST BORING AND RESISTIVITY SURVEY POSITIONING

Test boring depths and locations and resistivity survey locations for FTG217 were specified by USACE in the SOW and were staked by a USACE provided survey crew prior to field investigation activities. Three test borings required an additional alternate borehole location as described in Section 1.7. The location of these three additional alternate boreholes was determined via measurement of the horizontal offset and bearing from the original borehole location. As no survey drawing was available at the time of this report, these coordinates were then calculated within GIS environment by an R&M GIS Specialist for each of three boreholes.

Reported elevations of the staked locations for the 43 original test borings were provided by a USACE provided survey crew. Due to the extremely close proximity of the three alternate test boring locations to their original location and lack of any significant topography, reported elevations for the three additional alternate test borings were interpolated from the project survey drawing.

R&M facilitated underground utility locating at the project site through both the statewide utility clearance and Fort Greely Excavation Clearance Request/Approval processes prior to initiation of ground disturbance activities.

Locations of test borings drilled and resistivity surveys completed during the current investigation are presented in Appendix A on Drawing A-04. Coordinates and surface elevation information for the test borings completed during the investigation are provided in tabular form on Table 3-1, below, and on the test boring logs in Appendix B.

3.2 TEST BORINGS

R&M completed a total of forty-six (46) test borings, numbered AP-2879 through AP-2924, at the FTG217 project site during the period of November 3rd through November 18th, 2017. The depth of the test borings ranged from 9.0 to 112.4 feet bgs. Total footage drilled was approximately 2,800 lineal feet. The drilling program was conducted under the direct guidance of experienced R&M engineering geologists and geotechnical engineers who maintained detailed logs of the materials encountered and the samples collected. Each test boring was logged in accordance with standard engineering practices. Data obtained from the test borings were utilized for geologic interpretations. A key to the test boring log general notes, and an example of a typical log are illustrated in Appendix B on Drawings B-01, and B-02, respectively. The test borings logs are illustrated on Drawings B-03 through B-97. Table 3-1 and 3-2 provides a summary of the R&M test borings completed for this project.

January 2018 Page 14 R&M No. 2440.08

TABLE 3-1: SUMMARY OF R&M TEST BORINGS AP-2879 THROUGH AP-2906, FTG217

NOTES:

a Alaska State Plane Zone 3 NAD83 (horizontal) and NAVD88 (vertical), U.S. Survey Feet.

b Interpreted by R&M Geologist to have not been encountered while drilling.

c Calculated via horizontal offset and bearing from the originally intended location.

Test Boring

Number (Final)

Test Boring

Number (Field)

Coordinatesa Collar Elevationa, (Feet)

Total Depth (Feet)

Approximate Depth to

Groundwaterb (Feet)

Approximate Depth of

Permafrostb (Feet) Northing Easting

AP-2879 TB-01 3,639,767.1 1,686,936.5 1,346.2 82 NE NE

AP-2880 TB-01A 3,639,765.3c 1,686,937.7c 1,346.3 100 NE NE

AP-2881 TB-02 3,639,790.8 1,687,043.6 1,345.9 112.3 NE NE

AP-2882 TB-03 3,639,659.8 1,686,960.1 1,347.3 100.7 NE NE

AP-2883 TB-04 3,639,683.4 1,687,067.4 1,346.4 100.3 NE NE

AP-2884 TB-05 3,639,552.3 1,686,983.9 1,347.8 100.2 NE NE

AP-2885 TB-06 3,639,576.0 1,687,091.2 1,347.2 99.8 NE NE

AP-2886 TB-07 3,639,444.8 1,687,007.9 1,348.0 100 NE NE

AP-2887 TB-08 3,639,468.6 1,687,115.2 1,347.7 100 NE NE

AP-2888 TB-09 3,639,337.6 1,687,031.4 1,348.2 100.1 NE NE

AP-2889 TB-10 3,639,361.2 1,687,138.9 1,347.9 57 NE NE

AP-2890 TB-10A 3,639,363.7c 1,687,137.3c 1,347.7 100 NE NE

AP-2891 TB-11 3,639,230.0 1,687,055.5 1,349.0 100.5 NE NE

AP-2892 TB-12 3,639,253.8 1,687,163.0 1,349.0 100 NE NE

AP-2893 TB-13 3,639,122.5 1,687,079.3 1,349.5 100.2 NE NE

AP-2894 TB-14 3,639,146.3 1,687,186.5 1,349.3 100 NE NE

AP-2895 TB-15 3,639,015.4 1,687,103.2 1,350.8 101.3 NE NE

AP-2896 TB-16 3,639,039.2 1,687,210.7 1,349.4 100 NE NE

AP-2897 TB-17 3,638,908.0 1,687,127.1 1,351.8 100.8 NE NE

AP-2898 TB-18 3,638,931.6 1,687,234.4 1,350.2 100.8 NE NE

AP-2899 TB-19 3,638,800.4 1,687,150.7 1,352.4 100.5 NE NE

AP-2900 TB-20 3,638,824.2 1,687,258.1 1,350.8 101 NE NE

AP-2901 TB-21 3,638,466.0 1,687,199.5 1,352.8 51.5 NE NE

AP-2902 TB-22 3,638,485.3 1,687,285.4 1,352.5 51.5 NE NE

AP-2903 TB-23 3,638,399.8 1,687,214.2 1,353.5 51 NE NE

AP-2904 TB-24 3,638,418.8 1,687,300.1 1,353.2 51.5 NE NE

AP-2905 TB-25 3,638,442.4 1,687,249.8 1,352.7 112.4 NE NE

AP-2906 TB-26 3,639,823.3 1,687,189.2 1,344.8 16.5 NE NE

January 2018 Page 15 R&M No. 2440.08

TABLE 3-2: SUMMARY OF R&M TEST BORINGS AP-2907 THROUGH AP-2924, FTG217

NOTES:

a Alaska State Plane Zone 3 NAD83 (horizontal) and NAVD88 (vertical), U.S. Survey Feet.

b Interpreted by R&M Geologist to have not been encountered while drilling.

c Calculated via horizontal offset and bearing from the originally intended location.

Drilling and sampling operations were performed by Discovery Drilling, Inc. under contract with R&M, utilizing a combination of tracked CME-850 drilling rigs, a tracked CME-55 drilling rig, and a truck-mounted Mobile B-53 drilling rig. Representative photographs of drilling operations and site conditions are presented in Figure 3-1 and 3-2. Shallow test borings (0-50 feet) were accomplished using continuous-flight, 3 1/4-inch inside diameter (I.D.) by 6-inch outside diameter (O.D.) hollow-stem augers. Deep test borings (100-110 feet) were accomplished using 4-inch I.D. by 4.5-inch O.D.

drive casing advanced with a downhole…