Appendix_V_-_Geotechnical_Investigation.pdf

Transmittal To: Jacobs/Ammann & Whitney, JV Attn: Mr. Jeffrey S. Rubin

Address: 1100 N. Glebe Road, Suite 500 Date: June 14, 2012

Arlington, VA 22201 Job # 31-1-02277-001

Re: Consolidated Facilities Geotech

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1 PDF Geotechnical Study, Proposed Consolidated Facilities, Thule, Greenland

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Copies to: By: Steve Adamczak, Jr.

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2355 Hill Road Fairbanks, Alaska 99709-5326

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E-mail: sa@shanwil.com Alaska • Colorado • Illinois • Missouri • Oregon • Washington

GEOTECHNICAL STUDY

PROPOSED CONSOLIDATED FACILITIES

THULE, GREENLAND

June 2012

Submitted To:

Jacobs/Ammann & Whitney, JV

1100 N. Glebe Road, Suite 500 Arlington, VA 22201

By:

Shannon & Wilson, Inc.

2355 Hill Road

Fairbanks, Alaska 99709-5326

31-1-02277-001 i

TABLE OF CONTENTS

Page

1.0 INTRODUCTION

1.1 Project Understanding

1.2 Site-Specific Geotechnical Investigation and Report

2.0 GEOLOGIC AND SEISMIC SETTING

2.1 Geologic Setting and Physiography

2.2 Seismic Setting

3.0 CLIMATE

4.0 SITE CONDITIONS

4.1 Surface Conditions

4.2 Subsurface Conditions

5.0 EARTHQUAKE HAZARDS

6.0 GEOTECHNICAL DISCUSSION AND RECOMMENDATIONS

6.1 Additional Subsurface Exploration

6.2 Site Preparation

6.2.1 Excavation Slopes

6.2.2 Groundwater

6.3 Foundation Recommendations

6.4 Lateral Earth Pressures and Frictional Resistance

6.5 Thermal Analyses

6.5.1 Thermal Simulation Description

6.5.2 Air and Ground-Surface Temperatures

6.5.3 Material Properties and Initial Conditions

6.5.4 Thermal Simulation Results

6.6 Parking Areas and Driveways

6.7 Comments on Utilities

7.0 MATERIAL RECOMMENDATIONS

7.1 Structural Fill

7.2 Aggregate Surfacing

7.3 Nonstructural Fill

8.0 LIMITATIONS

9.0 REFERENCES

TABLE OF CONTENTS (cont.) SHANNON & WILSON ii

LIST OF FIGURES

Figure No.

1 Site Plan and Approximate Boring Locations 2 Mean Annual Air Temperature, Pituffik (Thule AB) Observing Station, 1952-2010 3 Air Freezing Index, Pituffik (Thule AB) Observing Station, 1952-2010 4 Air Thawing Index, Pituffik (Thule AB) Observing Station, 1952-2010 5 Calibration Temperature Profile 6 Simulated Air and Ground Surface Temperatures 7 Thermal Simulation (nf = 0.9 and nt = 1.5) 8 Typical Excavation Cross Section

LIST OF APPENDICES

Appendix

A CRREL Geophysical Investigation Report B Important Information About Your Geotechnical/Environmental Report

SHANNON & WILSON

GEOTECHNICAL STUDY

CONSOLIDATED FACILITIES

THULE AIR BASE, GREENLAND

1.0 INTRODUCTION

This report presents the results of our initial geotechnical exploration and engineering studies for the proposed Consolidated Vehicle Maintenance and Pavement & Grounds (Vehicle Maintenance) Facility; and Consolidated Civil Engineering Shops and Supply (CE Shops) Facility at Thule Air Base (Thule AB), Greenland. The purpose of our study was to interpret subsurface conditions from previous explorations at the proposed sites and prepare foundation, earthwork, and geotechnical construction recommendations for the planned structures.

Our study was conducted under Jacobs/Ammann & Whitney joint venture Subconsulting Agreement number FDWD5930-S11-0001, executed by Mr. Kevin R. McDonald.

1.1 Project Understanding

Both the CE Shops and Vehicle Maintenance Facilities are planned as approximately 50,000-square-foot, multi-story, steel framed buildings, currently scheduled for construction in fiscal years (FY) 2014 and 2015, respectively. Both projects will also include design and construction of associated parking areas, driveways, and utilities.

The CE Shops Facility has areas planned for various workshops (welding, carpentry, and construction), receiving/supply, and administration/support. The Vehicle Maintenance Facility has areas planed for vehicle maintenance (trucks, snowplows, and heavy equipment), storage, and administration/support.

The project sites are between North River and the runway, on the north side of Cresent Road, as shown in Figure 1. The CE Shops site is directly north of Hanger 10 (Building 630). The Vehicle Maintenance site is east of the CE Shops site, directly north of a pond and to the northeast of an existing gas station.

1.2 Site-Specific Geotechnical Investigation and Report

A site-specific geotechnical investigation was completed for the CE Shops Facility by Mr. Kevin Bjella, P.E., in 2011. Mr. Bjella is a Research Civil Engineer with the U.S. Army Corps of Engineers (USACE) Engineer Research and Development Center (ERDC) Cold Regions

Research and Engineering Laboratory (CRREL). The results of the investigation are presented in the ERDC/CRREL Letter Report LR 12-03 titled Thule Air Base, Consolidated Facilities, Permafrost and Geotechnical Investigation, January 20, 2012.

The subsurface explorations consisted of a Ground Penetrating Radar (GPR) survey in April, followed by six soil borings in August. The report summarizes exploration methods, surface and subsurface conditions encountered, and laboratory testing, and discusses some alternatives for foundation design.

The report states site conditions reported for the CE Shops Facility are generally applicable for the Vehicle Maintenance Facility due to their close proximity. The report cautions that while the conditions and stratigraphy of the soil and rock are not expected to change dramatically between the two sites, the depth and thickness of the units may vary and recommends a GPR survey be conducted for the Vehicle Maintenance Facility.

We used the findings presented in LR 12-03 as the basis of our design and have attached it as Appendix A. The approximate locations of the borings are presented in Figure 1.

2.0 GEOLOGIC AND SEISMIC SETTING

2.1 Geologic Setting and Physiography

Thule AB is in the geomorphic province known as the ‘Thule–Nûgssuaq Region,’ consisting of a glaciated coastal strip of land dominated by uplands and mountainous highlands with local ice caps. The area is underlain by two Precambrian rock types: highly metamorphosed shield rock overlain by unmetamorphosed sedimentary rocks of the Thule Supergroup consisting of a thick sequence of fluvial to shallow-marine sediments, and volcanic rock deposited in the Thule Basin (Dawes, P.R. 2006).

In the northwestern portion of the province, including Thule AB, the unmetamorphosed strata of the Thule Supergroup are exposed in the uplands. The area is generally ice-free, except for localized ice caps. Shield rocks outcrop southeast of the air base in an unglaciated margin along the Greenland Ice Sheet. A few limited lowland areas along the coast include areas of uplifted coastal plain and Quaternary-filled valleys such as the Pituffik Valley at Thule AB.

The outcrop pattern of Thule strata in the area is controlled by WNW-ESE to NW-SE-trending faults that split a 150-kilometer side region into tilted blocks representing half-grabens known as the Thule half-graben system. The system is composed of six half-grabens, each with bounding faults, along which Thule strata are downdropped relative to the block to the north. Within each block, the shield is overlain by southwesterly dipping Thule strata. Movements along the bounding faults are thought to be on the order of kilometers.

Within the half-grabens, smaller fault blocks occur, including both graben and horst structures;

these represent small to moderate displacements, which repeat strata levels within the same formation or group, as well as larger displacements affecting the map outcrop. The Thule strata form predominantly homoclinal, shallow-dipping sections, with anomalous inclinations caused by block faulting, tilting, drag folding, and regional flexuring. The rocks have not been regionally metamorphosed, but they are indurated and locally altered around volcanic dikes. At the project site, the sediments appeared to have a uniform shallow dip to the southwest, with anomalous inclinations that might be associated with nearby faulting.

The age of the Thule half-graben system is not tightly constrained, only bracketed by Quaternary deposits. It is thought the youngest movements may be associated with late Phanerozoic tectonism that affected the Baffin Bay region.

On South Mountain, the Thule half-graben system preserves the Narssârssuk Group of the Thule Supergroup. Formations of the Narssârssuk Group include multicolored progradational cycles of basal grey carbonates topped by red siltstones and sandstone.

The topography in the northwestern portion of the area around Thule AB results from tilted fault blocks of Thule strata, in which the more resistance lithologies dominated by sandstone, volcanic rock, and dolomite commonly form steep sea cliffs; the less-resistant argillaceous rocks form moderate slopes, except on interspersed sills where mesas and cuestas are common (i.e., Mount Dundas). Many valleys and fjords are fault-controlled; many coastlines have trends WNW to NW, parallel to the main structural blocks of the region.

The southeastern portion of the area consists of undulating dissected plateaus with dome-shaped mountains rising above a general elevation of 2,300 feet to 2,600 feet and steep fjord coasts. The highest ice-free summit is 3,716 feet at the margin of the ice sheet.

The area has been repeatedly glaciated, and lower elevations have been subject to marine transgressions due to changing sea levels. The entire region was likely overridden by the Greenland Ice Sheet during the last (Wisconsin) glacial maximum, with the glacier retreating 11,000 to 9,000 years ago.

On the rolling upland and plateau, there is a widespread surficial cover of boulder-rich glacial deposits modified by frost-shattering and solifluction. As the Greenland Ice Sheet retreated, it frequently left a blanket of drift composed primarily of ground moraine or glacial till (non-stratified drift) over the bedrock as a thin discontinuous veneer. Glaciofluvial material typically occurs in the broad river valleys and lowland plains (i.e., the Pituffik Valley). Colluvial deposits, including a wide variety of material types, occur on the lower reaches of upland slopes.

The tills, colluvium, and glaciofluvial deposits have been modified by permafrost and periglacial processes, including mechanical frost-shattering, frost-sorting, development of massive ice, thaw-unstable ice-rich soil, patterned ground, and solifluction.

Thule AB is in an arctic zone underlain by continuous permafrost, defined as ground that has remained at a temperature of 32 degrees Fahrenheit (°F) or less for two or more years. The maximum depth of permafrost in the Thule AB area is unknown, but could be greater than 1,000 feet. The thickness of the “active layer,” the portion of the ground at or near the surface that undergoes an annual freeze-thaw cycle, is largely dependent on the type of ground cover and snow depth, as well as other factors. Seasonal thaw depths at the site ranged from 5 feet to 8 feet bgs at the time of drilling.

The International Permafrost Association (IPA)’s Multi-Language Glossary of Permafrost and Related Ground-Ice Terms defines ice-rich permafrost as permafrost containing ice in excess of the pore space the ground would have under unfrozen conditions. Thaw-unstable or thaw-sensitive permafrost is defined as permafrost which, upon thawing, will experience significant thaw settlement and suffer loss of strength to a value significantly lower than similar material in an unfrozen condition.

2.2 Seismic Setting

Greenland is a relatively stable continental region with low seismicity. Its instrumentally recorded seismicity is concentrated along the ice-free coastlines; there are virtually no earthquakes recorded under the ice sheet. The most active region is along the northeast coast.

The largest recorded earthquake with a moment magnitude (mb) 5.5 occurred in the continental crust of the northeastern coast. It has been postulated earthquakes in northeastern Greenland are the result of stresses being transferred several hundred kilometers into the Greenland plate from shearing and spreading of the mid-ocean ridge in the Arctic Ocean with its transform faults.

Alternative hypothesis are that postglacial isostatic rebound of the deglaciated continental margin along the edge of the ice sheet and associated bending stresses in the lithosphere are reactivating historic faults. Seismicity along the west coast of Greenland is hypothesized to be the result of remnant stress from old tectonic movements, which divided Greenland from North America.

Poulsen and Simonsen (2006) conducted a seismic hazard analysis of Greenland using earthquake information constituting 227 events occurring from November 1971 to February 2006. The majority of these events had a magnitude between 3.0 and 5.0, but since 2005, improved analytical methods have lowered the detection threshold from 3.0 to 1.0 in some areas. The earthquakes depths were primarily shallow; most between 0 kilometers (km) to 40

km. They computed the seismic hazard for a return period of 475 years. The highest peak ground acceleration (PGA) for hard-rock ground conditions (0.051g) was found to be along the northeast coast of Greenland. In the Thule AB area, the PGA is around 0.024g. Poulsen and Simonsen conclude the general seismic hazard in Greenland is low.

3.0 CLIMATE

Climate and climate change is important to structures in permafrost areas. The earth’s climate has changed in the past and will continue to change in the future. It is recognized global recorded temperatures have increased on average approximately 1 °F in the last century. In arctic marine regions, the warming was about 1.7 °F. Global climate models through the end of the 21st century predict a warming for the entire Arctic of 6 °F to 12 °F. The warming is expected to be greatest during the colder seasons.

We obtained a climatological record for Thule AB from the Climate Research Center at the University of Alaska Fairbanks. For the record period, 1952 to 2010, mean annual temperature measured at the Base is 12.1 °F.

Air-temperature trends in the record are consistent with a projected warming of arctic regions.

The temperature departure from the long-term mean observed from 1952 to 2010 for Thule AB is shown in Figure 2. The period prior to 1995 was cooler, with a mean 0.7 °F colder than the long-term mean of 12.1 °F; 1995 to 2010 was warmer, with a mean 2.0 °F warmer than the long-term mean. The warming trends, analyzed in terms of freezing and thawing indices, suggest most of the change appears to be occurring during colder seasons (Figures 3 and 4). Increased air temperatures may result in permafrost warming, increased active-layer thickness, and an overall thinning of the permafrost.

4.0 SITE CONDITIONS

4.1 Surface Conditions

Both sites are largely undeveloped and in general, the topography slopes north towards North River approximately 700 feet away. The CE Shops site has been leveled with surficial gravel fills and used as a temporary storage/staging area. A culvert and concrete pipe run north under Cresent Road from an existing pond. The culvert empties into a swale; both the swale and concrete pipe cross the west end of the Vehicle Maintenance site, draining toward the North River.

We reviewed air photos of the site and noted a pond between the two sites in 2004, which was partially filled by 2010 (see Figure 1), leaving the swale described above.

4.2 Subsurface Conditions

The subsurface conditions described in the CRREL report consist of a silty gravel fill material underlain by ice-rich alluvial sand and gravel deposits containing massive ice, overlying highly to completely weathered shale bedrock increasing in competency with depth. Ice-poor shale bedrock appears to range from depths of approximately 16 feet to 23 feet below the ground surface (bgs); in general, the depth to bedrock increased from north to south.

Groundwater was not observed during drilling.

Massive ice formations were observed in two of the six boreholes. Approximately 12 feet of wedge-ice was encountered in Boring BH-2 and two 1.5-foot-thick layers of ice in Boring BH-3.

The depth of seasonal thaw ranged from 5 feet to 8 feet bgs at the time of drilling, which we anticipate is near maximum and likely represents the approximate depth of the active layer.

5.0 EARTHQUAKE HAZARDS

We assessed potential earthquake-induced geologic hazards that could affect the site, including fault rupture. The potential for fault rupture is considered low. The literature we reviewed does not recognize faults with Holocene displacement. Diffuse seismicity occurs along the ice-free coastlines; however, there are no patterns of measured seismicity in the Thule AB area that would indicate active faulting. The faulting associated with the Thule half-graben appears inactive. The seismicity of Greenland is not well understood; it is possible postglacial isostatic rebound of the deglaciated continental margin along the edge of the ice sheet may reactivate historic faults. Seismicity along the west coast of Greenland is hypothesized to be the result of remnant stress from old tectonic movements which divided Greenland from North America. The absence of obvious fault-related geomorphic structures does not preclude the possibility of active faults in the area.

The Unified Facilities Code (UFC) provides structural loading data for planning, design, and construction of buildings for the Department of Defense (DoD). The loading data includes available site-specific ground snow load, basic wind speed, seismic spectral accelerations, and frost penetration at significant DoD installations worldwide. The code adopts and modifies the 2006 International Building Code (IBC) as the building code for DoD projects. The information included in the code is intended to be a basis for applying the provisions of the UFC to significant DoD installations in and outside the United States.

We developed design ground motions from the maximum considered earthquake spectral response accelerations for the short period and 1-second (SS and S1) spectral responses from Table F-2 of UFC 3-301-01, January 2010, With Change 3, 31 January 2012 for Thule AB. The ground motion parameters are for Site Class B (Rock) conditions. Following the 2009 IBC, rock motions are adjusted for soil-amplification effects. We assumed the site will be excavated and filled with compacted structural fill material, which should have the characteristics of Site Class C (very dense soil or soft rock). Using this assumption, the spectral responses were adjusted to reflect Site Class C conditions. The design spectral response parameters are taken to be two-thirds of the adjusted value. We outline development of the design earthquake ground motion parameters in the following table:

EARTHQUAKE GROUND MOTION PARAMETERS

Description Parameter Value

Estimated soil shear wave velocity 1,200 ft/s to 2,500 ft/s

Site Class C Mapped spectral accelerations for 0.2 seconds (Site Class B, 5% damping)

Ss 0.37g

Mapped spectral accelerations for 1 second (Site Class B, 5% damping)

S1 0.15g

Site coefficient (Site Class C) Fa 1.2 Site coefficient (Site Class C) Fv 1.65 Ss adjusted for site class SMS 0.44g S1 adjusted for site class SM1 0.25g Design spectral response acceleration at short periods SDS 0.30g Design spectral response acceleration at 1-second period SD1 0.16g Peak ground acceleration PGA 0.12g

Peak ground acceleration (PGA) is taken as SDS/2.5.

6.0 GEOTECHNICAL DISCUSSION AND RECOMMENDATIONS

The CRREL subsurface investigations suggest bedrock at the site is covered with fill and alluvial deposits up to 23 feet deep. The CRREL studies note the alluvial soils are ice-rich and locally contain massive-ice formations. The underlying bedrock surface is reportedly weathered and likely disturbed by frost action (cryoturbation) and likely contains ice-rich zones and segregated ice. The underlying bedrock is interpreted to become more competent and ice-poor with depth.

Based on the CRREL subsurface investigations and our understanding of the geology of the site and experience with other projects at Thule AB, both sites should be considered to be underlain by ice-rich permafrost containing massive-ice formations. The primary geotechnical concern for both projects is permafrost degradation leading to loss of bearing and thaw-settlement.

In general, there are two options for reducing the risk of thaw-weakening/-settlement:

1) maintain thaw-unstable materials in a frozen condition by reducing heat flow from the buildings into the ground and removing heat from the ground through active or passive refrigeration; or 2) excavate and replace thaw-unstable materials with non-frost susceptible (NFS) fills.

Due to the size and planned use of the buildings, we recommend excavating and replacing thaw-unstable materials under the new structures with NFS fills to thaw-stable bedrock. The structures can then be founded at grade on thickened-edge-slabs or conventional spread and continuous footings bearing in the replacement fills. This approach has the least risk of adverse foundation performance over the life of the structures, as it does not rely on passive or active cooling systems to maintain the integrity of the foundations. We note this option will require large quantities of excavation and fill; however, we understand gravel fills are readily available in Thule. Our recommendations for site preparation and foundation design are presented in the following sections.

6.1 Additional Subsurface Exploration

As discussed above, existing subsurface explorations are limited to the CE Shops site and the CRREL report recommends a GPR survey be conducted for the Vehicle Maintenance Facility.

By excavating and replacing thaw-unstable materials under the new structures with NFS fills to thaw-stable bedrock, our design approach accounts for changes in the depth and thickness of unsuitable soils and rock between the two sites; however, it does not address cut-and-fill quantities for the Vehicle Maintenance Facility.

A subsurface drilling/coring program or GPR or other applicable geophysical survey may help approximate the depth to thaw-stable bedrock for the Vehicle Maintenance Facility and reduce risk when estimating cut-and-fill quantities.

6.2 Site Preparation

Site preparation should included excavating all thaw-unstable soils and rock from beneath the building footprints and extending out laterally a minimum of 10 feet beyond the outside edge of the footings. Based on the CRREL report, we anticipate the depth to ice-poor bedrock will be on the order of 16 feet to 23 feet bgs for the CE Shops facility. The depth to ice-poor bedrock in the area of the Vehicle Maintenance facility is unexplored; however, the CRREL report suggests it should be similar to the CE Shops facility.

Excavation of frozen soil and rock may be difficult to achieve with conventional equipment (e.g., a large excavator equipped with a standard bucket). Specialized equipment and methods, such as impact hammers, excavators with ripper teeth, dozers equipped with rippers, or drilling and blasting, may be required to complete the excavations. We recommend making the contractor responsible for excavation methods, as they will be familiar with the limitations of their equipment.

The base of the excavation should be relatively planar and not contain deep holes where undesirable soils or rock have been removed. Any material loosened in the excavation process should be removed prior to filling. Due to the limited subsurface explorations performed for the projects, we recommend an experienced engineer from our firm observe the excavations to determine whether conditions in the base are acceptable or if additional excavation is required to remove potentially thaw-unstable material. If additional localized excavation is required, the sides should be sloped no steeper than 4 horizontal to 1 vertical or benched, with bench heights equal to lift thickness and wide enough to accommodate compaction equipment prior to placing fill.

Once the excavation is complete, it should be filled with compacted lifts of structural fill as described in Section 7.1. The surface of the fill should be elevated above the surrounding ground to form pads. The edges of pads of structural fill may be constructed at slopes up to two horizontal to one vertical, starting a minimum of 10 feet from the edge of the building footprints.

The surface of the pads and surrounding ground should be sloped to provide positive drainage and prevent ponding of water on or near the pad. A typical excavation cross section is shown in Figure 8.

6.2.1 Excavation Slopes

All excavations should be sufficiently sloped or shored to provide a stable bank. We recommend the stability of the excavated slopes be made the responsibility of the contractor, as they will be most familiar with conditions encountered in the excavations and have direct control of working conditions at the site. The work should be accomplished in general accordance with applicable local, state, and federal standards. For planning purposes, we recommend assuming unsupported excavation slopes will be no steeper than one horizontal to one vertical. It is also important to note that temporary excavation slopes may initially stand steep, but slough and cave as they dry out, particularly when equipment is operated nearby. Similarly, frozen ground may allow for steep cuts to be made initially, but may become unstable upon thawing.

Maintaining the slopes in a frozen condition may allow for steeper excavation slopes, but will likely require some type of thermal mitigation system. Excessive thawing of the slopes could potentially be reduced by the use of thermally reflective construction blankets. Since Thule generally experiences cool nights, application of these blankets during the day may reduce the amount of solar energy absorbed by the slopes, reducing thaw-instability and sloughing.

6.2.2 Groundwater

While no groundwater was encountered during the subsurface explorations at the end of the summer season, significant quantities of groundwater were encountered during the Hangar 10 permafrost investigation, as described in the CRREL report. Groundwater in the area is likely heavily influenced by snow melt in the spring, when it may rise and flow along the top of the permafrost table. We recommend contractors be prepared to intercept groundwater in the active layer and keep the excavation dry, as flowing water can rapidly destabilize frozen cut slopes.

6.3 Foundation Recommendations

Thickened-edge-slabs or conventional spread and continuous footings bearing in thick sections of structural fill with a minimum depth of embedment of 2 feet may be designed for a maximum allowable bearing pressure of 4,000 pounds per square foot (psf). The minimum recommended width for spread footings and continuous footings, whether conventional or locally thickened portions of the slab, is 2 feet and 1.5 feet, respectively.

Building slabs should be constructed at-grade and consist of a minimum of 6 inches of Portland cement concrete (PCC). Building slabs may be designed using a modulus of subgrade reaction of 300 pounds per cubic inch (pci).

We estimate total settlements of less than 1 inch for foundations designed following these recommendations. Differential settlements between footings should be anticipated to be up to one-half of total settlements. We anticipate most of the settlement under static conditions will occur as structure loads are applied.

Although not necessary for frost protection, we recommend placing insulation around the outside of the foundations to control heat loss and maintain warm floors.

6.4 Lateral Earth Pressures and Frictional Resistance

Lateral earth pressures will develop against buried portions of structures and foundation walls.

The magnitude of the pressure will depend on the method of fill placement, type of fill, and water conditions. To estimate lateral earth pressures, we assumed a sand and gravel structural fill placed with a unit weight of 130 pcf and an internal angle of friction of 34 degrees.

At-rest earth pressures can develop against the walls during normal loading conditions, for which the walls are not anticipated to move relative to the surrounding ground. For this scenario, we recommend using an equivalent fluid weight of 57 pounds pcf to estimate lateral-earth pressures for structural fill.

Passive-earth pressures against buried portions of structures and friction along the base of buried portions of the structure can be used to resist lateral forces and movement. We recommend using an equivalent fluid weight of 460 pcf to estimate passive-earth pressures for structural fill.

During seismic loading, the equivalent fluid pressure should be reduced to 445 pcf. Frictional resistance against sliding along the base of foundations may be computed using a coefficient of friction of 0.59 between cast-in-place concrete and structural fill.

Depending on the sequence of construction and structural bracing, it is possible walls may rotate slightly during the placement and compaction of structural fill. If walls are allowed to rotate as little as 0.002H (where H is the height of the wall), they may be subjected to active-earth pressures rather than at-rest pressures. Active-earth pressure may be estimated as the static active-earth pressure plus a dynamic increment, distributed uniformly over the height of the buried portion of the structure. The static active-earth pressure should be estimated assuming an equivalent fluid weight of 37 pcf. We recommend using a dynamic increment of 12 percent of the static active-earth pressure.

The values presented in this section do not include a factor of safety.

6.5 Thermal Analyses

To assist us in assessing the potential impacts of the new facilities, we performed two-dimensional thermal simulations using Temp/W, a finite-element simulation package developed and sold by Geoslope International, Inc. We used the simulations to estimate permafrost degradation beneath and adjacent to the new structures with time. The simulation program was written to solve two-dimensional, nonsteady-state, heat-transfer problems with phase change. An apparent heat-capacity method is used to treat latent heat, which requires unfrozen moisture-content curves for materials undergoing phase change. Iteration is performed at every time-step to improve accuracy in establishing the phase-change boundary.

6.5.1 Thermal Simulation Description

We performed thermal simulations assuming the buildings will be founded on a 20-foot-thick section of structural fill overlying ice-poor shale bedrock, with side slopes cut through a soil profile based on the average findings of the CRREL borings. The mesh representing the constructed condition represents soil and rock to a depth of 60 feet bgs, extending 50 feet outside the building footprint. The vertical sides of the mesh were no-heat-flow boundaries. We developed air temperatures, used to drive the simulation, from historic air-temperature data for Thule AB. Ground-surface temperatures specified at the top of the mesh were developed by modifying air-temperature histories for anticipated surface conditions at the site.

We assumed a constant temperature boundary condition of 65 °F for the building slab. We set the boundary condition at the base of the fill to a constant unit-heat flux resulting in a geothermal gradient of 1°F/100 feet.

6.5.2 Air and Ground-Surface Temperatures

We developed air and ground-surface temperatures used in the models with climatological data for Thule AB, provided by the Alaska Climate Research Center (ACRC), for 1951 to 2010. The record is a compilation of temperatures from the first-order weather station at Pituffik, Greenland (Station 42020). A plot of the mean annual air temperature (MAAT) is shown in Figure 2.

From the mean daily temperatures, we calculated annual air freezing and thawing indices (AFI and ATI respectively), plotted in Figures 3 and 4. The temperature record shows a relatively abrupt warming or decrease in the mean AFI since 1996.

We selected the mean AFI and ATI for the period of warmer winters from 1996-2010 to develop mean daily air and ground-surface temperatures in the model. These indices are summarized in the following table:

SUMMARY OF AFI AND ATI (1996-2010)

Parameter AFI ATI

Mean 7349 827 Standard Deviation 473 205

We entered the selected design indices into the Alaska Department of Transportation & Public Facilities (ADOT&PF) Berg2 computer program to generate a sinusoidal relationship for daily air temperatures (Tair) in terms of MAAT and amplitude of the annual sinusoidal temperature cycle (A0) as follows:

)(2cos0 φπ tAMAATTair where t is in days, MAAT is in °F, and A0 is in °F.

We then modified the mean air temperature function for various surface conditions in Temp/W using n-factors for freezing and thawing (nf and nt) to describe surface-boundary conditions in the model (Figure 6).

We calibrated our model using the temperature profile presented in the CRREL report. We began with typical published n-factors for a gravel surface, with winter snow cover (i.e., nf = 0.9 and nt= 1.2) and modified them during calibration of the model to approximate thaw depth and recorded permafrost temperatures.

The results of the calibration runs are compared to the measured temperature profiles in Figure 5. Typical published n-factor values result in colder than anticipated ground temperatures with a shallower active layer. To approximate measured temperature profiles, we reduced the freezing n-factor and increased the thawing n-factor. Based on the calibration analysis, we selected nf = 0.65 and nt= 1.5 to represent the current gravel surface.

For the final analysis, we increased the freezing n-factor back to 0.9 to account for snow removal in parking areas around the new facilities.

6.5.3 Material Properties and Initial Conditions

We developed a generalized soil profile based on the CRREL explorations. We developed thermal properties based on soil type and laboratory testing; thermal conductivities for soils were determined by a method after Johansen (1975). The generalized soil profile and material properties we selected for use in the simulations are presented below:

SUMMARY OF MATERIAL PROPERTIES

Depth (feet)

Material

Dry Unit

Weight (lb/ft3)

Moisture Content

Unfrozen Thermal

Conductivity (Btu/h-ft-oF)

Frozen Thermal

Conductivity (Btu/h-ft-oF)

Unfrozen Heat

Capacity (Btu/ft3-oF)

Frozen Heat

Capacity (Btu/ft3-oF)

0 to 20 (inside excavation) NFS Fill 135 5 1.39 1.33 29.70 26.33

0 to 7 (outside excavation)

Silty/ Sandy Gravel Fill

120 10 1.22 1.42 32.4 26.4

7 to 10 (outside excavation)

Frozen Silty/ Sandy Gravel

90 33 0.96 1.82 45.00 30.15

10 to 20 (outside excavation)

Frozen Clay/ Weathered Shale

90 40 0.89 1.88 51.30 33.30

20 to 60 (entire site) Shale 159 5 1.83 2.76 34.98 31.01

Phase change and change in thermal conductivity were spread over a temperature range of 0.2 °F, from 31.8 °F to 32 °F.

6.5.4 Thermal Simulation Results

Using the parameters discussed above, we conducted simulations using excavation geometry and surface conditions. The simulations were run for a period of 20 years using one-day time-steps. We selected an initial temperature profile based on the temperature profile presented in the CRREL report. We modified the profile based on our experience to represent temperatures deeper than recorded in order to achieve a full profile for the initial condition. The simulation results are presented in Figure 7 for post-construction conditions.

We note that simulation results should be used as a guide, since there are uncertainties in our analyses. Additionally, there are uncertainties about future climatic conditions at this site and whether temperature trends will continue to increase over the life of the structure, remain at post- 1996 levels, or cool. For the purposes of our analyses, we have assumed they will remain at post- 1996 levels.

Over the 20-year simulation period, the model shows a stable active-layer thickness of about 5 feet to 7 feet outside the building footprint. Under the building, the thaw-bulb deepens over time, reaching a depth of 35 feet below current ground surface in five years and 50 feet in 20 years. Our thermal simulations indicate the lateral extent of the heat bulb from the buildings is contained within the structural fill, resulting in a low risk of building-induced thaw-settlement of adjacent ice-rich soils and lateral spreading of fill materials.

6.6 Parking Areas and Driveways

Pavement structures for aggregate-surfaced parking areas and driveways should consist of a minimum of 24 inches of structural fill. Depending on gradation, unconfined structural fill can shove and rut, especially if the particles are sub-rounded or rounded. In our experience, replacing the top 6 inches of aggregate-surfaced pavement structures with well-graded, crushed material containing between 8 percent and 15 percent fines greatly increases performance of the structure.

We have included recommendations for aggregate surfacing in Section 7.2. If there is a standard aggregate-surfacing material produced and used in Thule with satisfactory results, we recommend using that material.

6.7 Comments on Utilities

In permafrost areas, utility lines are commonly run above ground on pile supports, sleepers, or wooden cribbing. In the Thule AB cantonment area, we have observed utilities supported on wood cribbing and laying on the ground surface.

Connections to buildings or structures can be affected by the relative movement of the building and surrounding ground. If placement of utility lines below ground is desired in permafrost areas, the possibility of shearing of the lines at the penetration of the foundation wall due to permafrost degradation and thaw-settlement should be considered. If utility lines are placed in the active layer, frost-heave and settlement should be considered. If there is a potential for a belowground utility to be subject to differential frost-action, it should either be installed within a conduit large enough to isolate it from any possible shearing or tensile action or alternatively, be constructed above ground and enter the building through a conventional aboveground connection.

7.0 MATERIAL RECOMMENDATIONS

7.1 Structural Fill

Structural fill should consist of unfrozen, NFS gravelly sand or sandy gravel meeting the following gradation limits after compaction:

GRADATION CRITERIA FOR STRUCTURAL FILL

Size Percent Passing

4-inch 100

No. 4 sieve 30-60

No. 200 sieve 0-6

To our knowledge, the primary sources of NFS construction aggregate in the Thule AB area are glacial outwash sands and gravels in the valley bottom and basalt sills and dykes in upland areas.

The igneous material has been a source of crushed material. We have observed construction aggregate used to build foundation pads on past projects in Thule consisting of a graded gravelly material with subangular to subrounded particles. The material appears to have been imported from material sources in the valley bottom or screened from glacial drift covering the nearby mountains. Any of these sources would be acceptable for this project.

Structural fill should be placed in layers not exceeding 8 inches in loose height, moisture conditioned, and compacted with large, self-propelled vibratory rollers. The material in each layer should be compacted to achieve a density of at least 95 percent of the maximum dry density based on the Modified Proctor moisture-density relationship (ASTM International [ASTM] D1557). In-place densities and water contents of the soil should be measured using nuclear methods (ASTM D6938). The fill should consist of unfrozen materials placed at above-freezing air temperatures. Thermal covers and or heated blankets could be used to keep fill from freezing. If previously placed fill does freeze, for instance overnight, the frozen material should be excavated and wasted or allowed to thaw and recompacted prior to the placement of additional fill. We recommend using hand-operated equipment within in 5 feet of existing foundations or structures.

ASTM D6938 uses a nuclear densitometer to measure density; ASTM D1557 is a laboratory-determined reference density. Logistically, transporting an instrument with a nuclear source to Thule AB or a bulk sample to a laboratory in the US for density testing may be difficult.

The laboratory equipment needed for ASTM D1557 could be shipped to Thule AB and in-place densities could be determined by the sand-cone (ASTM D1556) or rubber-balloon methods

(ASTM D2167).

In lieu of conventional compaction control, a test section could be used to develop compaction methods and effort to be used during construction. Compaction during construction should be then be controlled by visually observing methods and effort including: moisture control, lift thickness, number of passes, changes in material or material source, and resistance to rutting or penetration.

The methods should be established in a test section with density determined using ASTM D1556, ASTM D2167, or ASTM D5030 (Density of Soil and Rock in Place by Water Replacement). ASTM D5030 uses a relatively large test pit lined with plastic and filled with water to measure in-place densities. ASTM D5030 is only recommended when used in conjunction with the test section/method approach. Testing would establish:

• compactor size;

• number of passes;

• minimum lift thickness; and

• moisture control.

The contractor should prepare a compaction plan and submit it to the engineer before mobilizing to the site.

7.2 Aggregate Surfacing

If used, aggregate surfacing should consist of unfrozen crushed stone or crushed gravel consisting of sound, tough, durable particles of uniform quality meeting the following gradation limits after compaction:

GRADATION CRITERIA FOR CRUSHED AGGREGATE SURFACING

Size Percent Passing

1-inch 100

3/4-inch 70-100 3/8-inch 50-85 No. 4 sieve 35-65 No. 8 sieve 20-50

No. 50 sieve 15-30

No. 200 sieve 8-15

Aggregate surfacing should be compacted with large, self-propelled vibratory rollers and placed in layers not exceeding 6 inches in loose height; the material in each layer should be moisture-conditioned and compacted to achieve a density of at least 95 percent of the maximum density obtained by ASTM D1557 or in a similar manor to structural fill.

7.3 Nonstructural Fill

Nonstructural fills may be used to fill or shape non-trafficked areas. Nonstructural fills may consist of silt or silty soils from the excavations; however, the fill should not contain topsoil or organics. Maximum loose lift height for nonstructural fill should not exceed 1 foot. This material should be moisture-conditioned and compacted to at least 90 percent of the maximum density obtained by ASTM D1557 or in a similar manor to structural fill.

8.0 LIMITATIONS

Subsurface explorations and testing will identify subsurface conditions only at those points where samples are taken, and at the time they are taken. Actual conditions at other locations of the project site, including those inferred to exist between the sample points, may differ significantly from conditions existing at the sampling locations. The passage of time or intervening causes may change the actual conditions at the sampling locations as well.

Interpretations and recommendations made by Shannon & Wilson are based solely upon information available to Shannon & Wilson at the time the interpretations and recommendations are made.

This report was prepared for the exclusive use of our client. All documents prepared by Shannon & Wilson are instruments of service with respect to the project for the sole use of the design-construct team. Only our team shall have the right to rely upon such documents. Such documents are not intended or represented to be suitable for reuse. Any such reuse without written verification or adaptation by Shannon & Wilson, as appropriate for the specific purpose intended, shall be at the user’s sole risk.

Copies of documents that may be relied upon by our Client are limited to the printed copies (also known as hard copies) signed or sealed by Shannon & Wilson. Text, data, or graphics files in electronic media format are furnished solely for the convenience of our Client. Any conclusion or information obtained or derived from such electronic files shall be at the user’s sole risk. If there is a discrepancy between the electronic files and the hard copies, the hard copies govern.

Because data stored in electronic media can deteriorate or be modified inadvertently or otherwise without authorization of the data’s creator, the Client should perform acceptance tests or procedures within 60 days after its receipt, after which, unless notice of any errors are given in writing to Shannon & Wilson, the Client shall be deemed to have accepted the data thus transferred. Any errors reported within the 60-day acceptance period shall be corrected by Shannon & Wilson. Shannon & Wilson shall not be responsible for maintaining documents stored in electronic media format after acceptance by the Client.

When transferring documents in electronic media format, Shannon & Wilson does not make any representations as to long-term compatibility, usability, or readability of documents resulting from the use of software application packages, operating systems, or computer hardware differing from those used for the document’s creation.

Shannon & Wilson, Inc., has prepared the attachment Important Information About Your Geotechnical/Environmental Report in Appendix B to assist you and others in understanding the uses and limitations of our reports.

9.0 REFERENCES

Bjella, K. 2012. Thule Air Base Consolidated Facilities Permafrost and Geotechnical Investigation. ERDC-CRREL Letter Report LR 12-03.

Chung, W. and Gao, 1997: H. The Greenland earthquake of 11 July 1987 and postglacial fault reactivation along a passive margin. Bulletin of the Seismological Society of America, Vol. 87, No. 4, 1058-1068.

Dawes, P.R. 2006: Explanatory notes to the Geological map of Greenland, 1:500 000, Thule, Sheet 5. Geological Survey of Denmark and Greenland Map Series 2, 97 pp. + map.

Department of Defense, 2010, UFC 3-130-04: Unified Facilities Criteria: Foundations for Structures: Arctic and Subarctic Construction.

Department of Defense, 2010, UFC 3-301-01: Unified Facilities Criteria: Structural engineering.

Gregersen, S. 2006: Intraplate earthquakes in Scandinavia and Greenland. Neotectonics or postglacial uplift. Journal of Indian Geophysical Union 10, 25-30.

Gregersen, S. 1982: Earthquakes in Greenland. Bulletin of the Geological Society of Denmark, Vol. 31, 123-27.

International Code Council, 2009, International Building Code.

Kurtz, K. & Wales, D.B. 1950: Geology of the Thule Area, Greenland. Proceedings of the Oklahoma Academy of Science for 1950, 83-89.

Poulsen, S.K. & Simonsen, S.B. 2006: Seismic Hazard Analysis of Greenland and Distribution of Earthquakes.

Voss, P., and others. 2007: Seismic hazard assessment of Greenland. GEUS Geological Survey of Denmark and Greenland Bulletin 13, 57-60.

Legend

Approximate CRREL Boring Location and Number-

NOT TO SCALE

BH-1

SITE PLAN AND

APPROXIMATE BORING LOCATIONS

Geotechnical Study

Proposed Consolidated Facilities

Thule Air Base, Greenland

31-1-02277-001

VEHICLE MAINTENANCE BUILDING

CE SHOPS

BUILDING

BH-1

BH-2

BH-3 BH-4

BH-5

BH-6

Figure 1

HANGAR 10

HANGAR 9

Map adapted from aerial imagery provided by Google Earth Pro, reproduced by permission granted by

Google Earth ™ Mapping Service.

NORTH RIVER

TAXIWAY

Previous Extent of Pond

CRESENT ROAD

-7

-6

-5

-4

-3

-2

-1

Negative Departure

Positive Departure

5-year Moving Average

Legend:

Geotechnical Study

Proposed Consolidated Facilities Thule Air Base, Greenland

MEAN ANNUAL AIR TEMPERATURE

PITUFFIK (THULE AB)

OBSERVING STATION

1952-20102012 31-1-02277-001 Figure 2

M ea n An nu al

T em pe ra tu re

D ep ar tu re

F)

Mean Air Temperature:

1952-2010 12.1°F (basis of figure) 1952-1995 11.4°F 1996-2010 14.1°F

-1,800

-1,400

-1,000

-600

-200

1,000

1,400

1,800

Negative Departure

Positive Departure

5-year Moving Average

Legend:

Geotechnical Study

Proposed Consolidated Facilities Thule Air Base, Greenland

AIR FREEZING INDEX (AFI)

PITUFFIK (THULE AB)

OBSERVING STATION

1952-20102012 31-1-02277-001 Figure 3

M ea n An nu al

F re ez in g In de x

D ep ar tu re

F-da ys

Mean Freezing Index ( F-days):

1952-2010 7,961°F-days (basis of figure) 1952-1995 8,186°F-days 1996-2010 7,349°F-days

-1,800

-1,400

-1,000

-600

-200

1,000

1,400

1,800

Negative Departure

Positive Departure

5-year Moving Average

Legend:

Geotechnical Study

Proposed Consolidated Facilities Thule Air Base, Greenland

AIR THAWING INDEX (ATI)

PITUFFIK (THULE AB)

OBSERVING STATION

1952-20102012 31-1-02277-001 Figure 4

M ea n An nu al

T ha w in g In de x

D ep ar tu re

F-da ys

Mean Thawing Index ( F-days):

1952-2010 722°F-days (basis of figure) 1952-1995 684°F-days 1996-2010 827°F-days

10 20 30 40 50 w G ro un d Su rfa ce

(f ee

t) Temperature (oF)

D ep th B el ow

TEMP/W (nt=1.5 and nf=0.75)

CRREL (9/20/11)

32 degree isotherm

Geotechnical Study Proposed Consolidated Facilities

Thule Air Base, Greenland

CALIBRATION TEMPERATURE

PROFILE

2012 31-1-02277-001 Figure 5

-20

-10

Te m pe ra tu re

(⁰ F)

Mean Air Temperature (1996 to 2010)

Simulated Mean Air Temperature

Simulated Ground Surface Temperature (nt=1.5, nf=0.9)

32 Degree Isotherm

Legend: Geotechnical Study Proposed Consolidated Facilities

Thule Air Base, Greenland

SIMULATED AIR AND GROUND SURFACE

TEMPERATURES

2012 31-1-02277-001

Figure 6

Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec.

Not to Scale

Distance (feet)

E le va tio n fe e t)

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270

-110

-105

-100

-95

-90

-85

-80

-75

-70

-65

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

Distance (feet)

D e p th fe e t)

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

D e p th

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

-5

-10

-15

-20

-25

-30

-35

-40

-45

-50

-55

-65

-60

-70

32-degree Isotherms

1°F/100 feet Flux Boundary

Constant-

Zero Heat- Flow Boundary

Zero…